Stormwater recovery for irrigation?

[dragoncar]

As previously mentioned, my water bills are crazy high.  We have a storm drain on the property that seems to have some flow even during dry periods.  Part of me thinks I should set up a pump (it's at least 15 feet down) to try to use that flow to water my drought intolerant plants.  Any ideas?  Would it even be worth it, factoring the electricity for the pump?  Is it ... legally questionable (it's on my property, but the county has a storm drain easement)?

[The Architect]

Is it ... legally questionable (it's on my property, but the county has a storm drain easement)?

Yes, it's probably legally questionable. Will you get caught? Probably not. Need to know your area to know for sure though. A few storm barrels are probably easier and cheaper, and might help significantly (does it ever rain where you live? Snow?); they too might be legally questionable depending on where you live though.

[dragoncar]

Is it ... legally questionable (it's on my property, but the county has a storm drain easement)?

Yes, it's probably legally questionable. Will you get caught? Probably not. Need to know your area to know for sure though. A few storm barrels are probably easier and cheaper, and might help significantly (does it ever rain where you live? Snow?); they too might be legally questionable depending on where you live though.

It's California, so the issue is it doesn't rain at all in summer.  A couple barrels wouldn't really help.  I'll likely get really good savings by just watering less, after I titrate my plants off their currently excessive schedule (3 times a week).  But I'm not entirely certain how to do that without killing them....  I know little about plants.

[nereo]

Any ideas?

Rain barrels may be impractical, but could you install/use a cistern?  When I lived in California my neighbor had one that collected rainwater off his roof - I think it held ~4,000 gallons, which he then used during the summer and fall.

[dragoncar]

Any ideas?

Rain barrels may be impractical, but could you install/use a cistern?  When I lived in California my neighbor had one that collected rainwater off his roof - I think it held ~4,000 gallons, which he then used during the summer and fall.

Possibly, but in that case it wouldn't be very different from pumping the storm drain.  How much does it cost to install such a system?

[nereo]

Any ideas?

Rain barrels may be impractical, but could you install/use a cistern?  When I lived in California my neighbor had one that collected rainwater off his roof - I think it held ~4,000 gallons, which he then used during the summer and fall.

Possibly, but in that case it wouldn't be very different from pumping the storm drain.  How much does it cost to install such a system?

haven't installed one myself, but it depends a lot on what you're looking for.  below-ground cisterns are complex and expensive, needing excavation and a sump and venting.  But if you can put an above-ground cistern close to your house it's pretty straightforward - all you need is a large holding tank and some pipes to connect your downspouts to the tank.  That's what my neighbor installed.  New, pre-made tanks start at several hundred$, but there's often agricultural/veinyard cast-offs on craigslist (often simply listed as a 'tank').  Or you can build-your-own with masonry walls and a liner.  We were considering doing something before we abruptly left central California.
google "DIY cistern" - entire forums out there explaining how to do it.

oh - and depending on your municipality they may be 'legally questionable.'  But - IMO what falls on your roof you should be able to save for a few months anyway.

[The Architect]

It's California, so the issue is it doesn't rain at all in summer.  A couple barrels wouldn't really help.  I'll likely get really good savings by just watering less, after I titrate my plants off their currently excessive schedule (3 times a week).  But I'm not entirely certain how to do that without killing them....  I know little about plants.

Rain barrels may be impractical, but could you install/use a cistern?  When I lived in California my neighbor had one that collected rainwater off his roof - I think it held ~4,000 gallons, which he then used during the summer and fall.

Four 55-gallon drums hooked up to your downspouts on the corners of your house would hold 220 gallons. If you have more downspouts, putting more drums out would give you more storage. You can definitely DIY that and it'd be cheaper than a cistern. Put a hose bib on the bottom of each barrel or get barrels with them pre-installed and you're good to go. Otherwise, you'll be looking at installing a huge tank and running/pumping all your runoff into it, which is possible to DIY but probably would be better with a pro.

Or look into Xeriscaping.

[TrMama]

Runoff from storm drains is often super polluted. As in, when storm drains empty into the ocean they kill everything in the vicinity. If you used this water on your garden there's a good chance it would kill your plants.

[PhysicsCat]

Four 55-gallon drums hooked up to your downspouts on the corners of your house would hold 220 gallons. If you have more downspouts, putting more drums out would give you more storage. You can definitely DIY that and it'd be cheaper than a cistern. Put a hose bib on the bottom of each barrel or get barrels with them pre-installed and you're good to go. Otherwise, you'll be looking at installing a huge tank and running/pumping all your runoff into it, which is possible to DIY but probably would be better with a pro.

You can actually double that (or more) by having 2 tanks side by side with the first set up a little higher and connected to the downspout with a bit of pipe near the top connected to the second tank so that it fills the other once the first is full. Of course with this set up you're looking at only 440 gallons max which isn't really going to put a dent in your water bill assuming dry/wet season.

[Glenstache]

Could the problem also be landscaping with non-native plants that are not drought tolerant? Over the long term, drought is the future of California and adapting to that reality may be more cost-effective over the long term.

[dragoncar]

Could the problem also be landscaping with non-native plants that are not drought tolerant? Over the long term, drought is the future of California and adapting to that reality may be more cost-effective over the long term.

Sure, I've planted a lot of natives, but free water seems like a good way to keep existing landscaping alive.

Four 55-gallon drums hooked up to your downspouts on the corners of your house would hold 220 gallons. If you have more downspouts, putting more drums out would give you more storage. You can definitely DIY that and it'd be cheaper than a cistern. Put a hose bib on the bottom of each barrel or get barrels with them pre-installed and you're good to go. Otherwise, you'll be looking at installing a huge tank and running/pumping all your runoff into it, which is possible to DIY but probably would be better with a pro.

You can actually double that (or more) by having 2 tanks side by side with the first set up a little higher and connected to the downspout with a bit of pipe near the top connected to the second tank so that it fills the other once the first is full. Of course with this set up you're looking at only 440 gallons max which isn't really going to put a dent in your water bill assuming dry/wet season.

Yeah the first month was 17000 gallons (on automatic) so no dent there.  I'm manually running things now, so not sure what my long term needs will be.  Looking into a system with moisture sensor as my clay soil holds moisture pretty well.  But there's also some kind of leak in the irrigation lines that would need to be resolved which sounds like a major pita

[Prairie Stash]

What's the price of your water? As in $/cf or $/gallon.  Then estimate how many times it rains and would fill your barrel/year. Does a rain barrel make sense still?

I did the math and estimated I can save about $1/year/barrel for each water barrel I install. Sure I can install multiple barrels in a row, I just pay for some connectors and barrels.  It might only cost $20 for the barrel and connectors, barrels are listed online for $15-20, maybe I can find a better deal. It's still a 20 year payback for me, if everything goes according to plan. Currently I'm on the lookout for free supplies, I don't mind waiting.

I wouldn't use storm sewer runoff, in my area it contains elevated levels of salt, oils, pesticides, herbicides and whatever else people decide to dump. Over the long term those things accumulate and can be toxic to plants.

[The Architect]

You can actually double that (or more) by having 2 tanks side by side with the first set up a little higher and connected to the downspout with a bit of pipe near the top connected to the second tank so that it fills the other once the first is full. Of course with this set up you're looking at only 440 gallons max which isn't really going to put a dent in your water bill assuming dry/wet season.

Or you could get bigger barrels. Shouldn't be hard to find several hundred gallon tanks; look around at farm supply places.

Could the problem also be landscaping with non-native plants that are not drought tolerant? Over the long term, drought is the future of California and adapting to that reality may be more cost-effective over the long term.

Sure, I've planted a lot of natives, but free water seems like a good way to keep existing landscaping alive.

Yeah the first month was 17000 gallons (on automatic) so no dent there.

Did you look into xeriscaping?

[dragoncar]

Did you look into xeriscaping?

Sure, I've planted a lot of natives, but free water seems like a good way to keep existing landscaping alive.

[Spondulix]

Have you looked into a laundry greywater system? That's another good way to water shrubs, trees, etc. If you know how to do sprinkler stuff (glue PVC, etc) it's totally manageable to do yourself.

[sol]

Pumping out of a storm drain?  WTF?

1.  Very illegal.  Everywhere in the US, anyway.

2.  Very unhealthy.  Stormwater is every city's biggest pollution problem.  Please don't put it on your yard.

3.  Very ridiculous.  You're worried about your water bill, but your first thought is theft rather than conservation?  Grow up.

[deborah]

Keeping your own storm water on your property and removing the pollutants from it is a worthwhile thing to do. Melbourne Water has a lot of information on rain gardens - see http://www.melbournewater.com.au/raingardens - gardens that take the storm water from your own roof and use it in your own garden.

This is an alternative to rain water tanks, and would enable you to harvest much of the water from your roof. One thing that is not mentioned is a sump. Dig a hole in a lower part of your garden 1 yard x 1yard x 1yard and fill it with scoria (you will obviously need 1 cubic yard of scoria. Snake drainage pipes through your garden ending at the sump (you will of course make the contour right so they gently fall toward the sump. Plant the things that heed the most water around your sump. You could, of course,  have the drainage pipes going from your rain gardens to the sump rather than back into the storm water system as per the Melbourne Water plans. Just make sure that you will never flood one of your neighbours.

[sol]

Keeping your own storm water on your property and removing the pollutants from it is a worthwhile thing to do.

Sure, this is common practice here too.  This is very different from what the OP suggested, which was putting a pump hose down his sewer grate to remove water.

[deborah]

Keeping your own storm water on your property and removing the pollutants from it is a worthwhile thing to do.

Sure, this is common practice here too.  This is very different from what the OP suggested, which was putting a pump hose down his sewer grate to remove water.

Agreed - just giving alternatives to tanks.

There are places in cities here where there is no storm water system because of the amount of pollution it causes, and everyone has to have sumps on their property.

[dragoncar]

Pumping out of a storm drain?  WTF?

1.  Very illegal.  Everywhere in the US, anyway.

2.  Very unhealthy.  Stormwater is every city's biggest pollution problem.  Please don't put it on your yard.

3.  Very ridiculous.  You're worried about your water bill, but your first thought is theft rather than conservation?  Grow up.

Duuuuude.... I don't know if it's illegal here.  But I do know that stormwater runs directly to the bay (so says the "no dumping" sign on my curb), or in nearby cities to the water processing plant (which overflows raw sewage into the bay during heavy rains).  Most municipalities are installing bioswales to reduce the amount of water entering the stormwater system.  So I see no moral issue with using the water.   If anything, this seems beneficial for everyone involved (unless the polluted water kills my plants?).  So grow up yerself!

[deborah]

Pumping out of a storm drain?  WTF?

1.  Very illegal.  Everywhere in the US, anyway.

2.  Very unhealthy.  Stormwater is every city's biggest pollution problem.  Please don't put it on your yard.

3.  Very ridiculous.  You're worried about your water bill, but your first thought is theft rather than conservation?  Grow up.

Duuuuude.... I don't know if it's illegal here.  But I do know that stormwater runs directly to the bay (so says the "no dumping" sign on my curb), or in nearby cities to the water processing plant (which overflows raw sewage into the bay during heavy rains).  Most municipalities are installing bioswales to reduce the amount of water entering the stormwater system.  So I see no moral issue with using the water.   If anything, this seems beneficial for everyone involved (unless the polluted water kills my plants?).  So grow up yerself!

Yes, it may kill your plants. If it is off the street it will have oil and petrol mixed in it, and if it is off some people's roofs it may have some chemicals in it that plants dont like. Bio-swales and rain gardens usually include specific plants that grow better than others in polluted environments - depending upon the pollutant expected in the bio-swale. If you take what's in the drain, everything will be mixed, and you probably have no idea of the pollutants involved and you certainly don't want to put it on your vegetables in case it includes feces or heavy metals. You may end up polluting your soil. People who have their block of land innundated by floods often need to get their block of land fixed because it has been polluted.

[Zette]

Where in CA do you live?  San Diego only gets about 10 inches of rain PER YEAR -- you wouldn't get much water from rain barrels here.  The laundry grey-water recycling sounds interesting, and of course changing your plantings out to draught-tolerant and native varieties reduces your water needs considerably. 

[dragoncar]

Where in CA do you live?  San Diego only gets about 10 inches of rain PER YEAR -- you wouldn't get much water from rain barrels here.  The laundry grey-water recycling sounds interesting, and of course changing your plantings out to draught-tolerant and native varieties reduces your water needs considerably.

Yeah rain barrels seem silly to me

Pumping out of a storm drain?  WTF?

1.  Very illegal.  Everywhere in the US, anyway.

2.  Very unhealthy.  Stormwater is every city's biggest pollution problem.  Please don't put it on your yard.

3.  Very ridiculous.  You're worried about your water bill, but your first thought is theft rather than conservation?  Grow up.

Duuuuude.... I don't know if it's illegal here.  But I do know that stormwater runs directly to the bay (so says the "no dumping" sign on my curb), or in nearby cities to the water processing plant (which overflows raw sewage into the bay during heavy rains).  Most municipalities are installing bioswales to reduce the amount of water entering the stormwater system.  So I see no moral issue with using the water.   If anything, this seems beneficial for everyone involved (unless the polluted water kills my plants?).  So grow up yerself!

Yes, it may kill your plants. If it is off the street it will have oil and petrol mixed in it, and if it is off some people's roofs it may have some chemicals in it that plants dont like. Bio-swales and rain gardens usually include specific plants that grow better than others in polluted environments - depending upon the pollutant expected in the bio-swale. If you take what's in the drain, everything will be mixed, and you probably have no idea of the pollutants involved and you certainly don't want to put it on your vegetables in case it includes feces or heavy metals. You may end up polluting your soil. People who have their block of land innundated by floods often need to get their block of land fixed because it has been polluted.

Yeah, pollution probably kills this idea.  Likely there is nothing too bad as there are very few houses and a nature preserve uphill from me. 

If it was only about plants dying, I'd still try it.  Because to completely xeriscape, I'd have to kill toes plants anyways, right? 

But I agree it's not worth potentially concentrating heavy metals in my own soil.

[Mrs. PoP]

Where in CA do you live?  San Diego only gets about 10 inches of rain PER YEAR -- you wouldn't get much water from rain barrels here.  The laundry grey-water recycling sounds interesting, and of course changing your plantings out to draught-tolerant and native varieties reduces your water needs considerably.

Laundry grey water isn't legal to use for landscaping everywhere.  I looked into it for us recently and it's a huge No-No in Florida and I think it's due to potential phosphates entering the waterways.  Make sure you check into the legality even if it would be an easy DIY.

[dragoncar]

Where in CA do you live?  San Diego only gets about 10 inches of rain PER YEAR -- you wouldn't get much water from rain barrels here.  The laundry grey-water recycling sounds interesting, and of course changing your plantings out to draught-tolerant and native varieties reduces your water needs considerably.

Laundry grey water isn't legal to use for landscaping everywhere.  I looked into it for us recently and it's a huge No-No in Florida and I think it's due to potential phosphates entering the waterways.  Make sure you check into the legality even if it would be an easy DIY.

Laundry would provide approximately 7 gallons per week at my current usage.  It's not nothing, but it's low enough to qualify as turd polishing IMO

[nereo]

Where in CA do you live?  San Diego only gets about 10 inches of rain PER YEAR -- you wouldn't get much water from rain barrels here.  The laundry grey-water recycling sounds interesting, and of course changing your plantings out to draught-tolerant and native varieties reduces your water needs considerably.

actually, even in areas like San Diego using storage tanks can be effective.  10" of rain is equal to 6.23 gallons of water falling on every square foot of roof.  That means on a typical roof of 1,500ft3 you can collect over 9,000 gallons of water from just 10" of annual rain.  If you wanted to use that collected rainwater for 6 months of the year you could use 350 gallons/week, or about 70 gallons every single day.

It's a lot of water.  Perhaps not as much as DragonCar's current usage, but more than what most gardens need.

[dragoncar]

Where in CA do you live?  San Diego only gets about 10 inches of rain PER YEAR -- you wouldn't get much water from rain barrels here.  The laundry grey-water recycling sounds interesting, and of course changing your plantings out to draught-tolerant and native varieties reduces your water needs considerably.

actually, even in areas like San Diego using storage tanks can be effective.  10" of rain is equal to 6.23 gallons of water falling on every square foot of roof.  That means on a typical roof of 1,500ft3 you can collect over 9,000 gallons of water from just 10" of annual rain.  If you wanted to use that collected rainwater for 6 months of the year you could use 350 gallons/week, or about 70 gallons every single day.

It's a lot of water.  Perhaps not as much as DragonCar's current usage, but more than what most gardens need.

If you could capture it all, yes.  But in CA most of that rain comes down in Jan-March, during which your barrels will be overflowing and you won't need to supplement water at all.  Then, by the end of April your barrels are empty and you have another 6 months before more rain.

[deborah]

Depends on how big your tanks are. A fantastic book I have "Making your home sustainable - A Guide to Retrofitting" by Derek Wrigley suggests that up to 10% of rainfall does not make it to the roof gutter - it might be vaporized when it falls onto a hot roof, and after rainfall a roof is glistening with water that just stays there. If you are collecting water from a roof, the first few gallons needs to be tossed away because it is full of muck from the roof, will settle into the bottom of your tank, and eventually clog it up completely. About 10% of the water in a tank in summer gets evaporated. And of course, climate scientists expect rainfall to decrease with climate change (in my area it is more than 5%). So it is a bit silly to expect that you can use the entire rainfall for irrigation.

Because of the evaporation, and the fact that San Diego has a Mediterranean climate (wet winters, dry summers), it might be best to bury a tank (or use a sump, like I suggested above).

[Spondulix]

If you could capture it all, yes.  But in CA most of that rain comes down in Jan-March, during which your barrels will be overflowing and you won't need to supplement water at all.  Then, by the end of April your barrels are empty and you have another 6 months before more rain.

It's funny cause Los Angeles DWP is offering a huge rebate for rain barrels right now ($100 each up to 4, so $400 total)... which I wonder if that's why this conversation is coming up. I may get a couple since it'll cost me nothing.

Laundry to landscape is legal without a permit in LA county. I went to a free workshop to learn how to do it, and have my system mostly setup, but not running yet. The parts weren't cheap (it ended up being maybe $100), but it's going to take like 1/4 of my front yard completely off the sprinkler system.

[dragoncar]

If you could capture it all, yes.  But in CA most of that rain comes down in Jan-March, during which your barrels will be overflowing and you won't need to supplement water at all.  Then, by the end of April your barrels are empty and you have another 6 months before more rain.

It's funny cause Los Angeles DWP is offering a huge rebate for rain barrels right now ($100 each up to 4, so $400 total)... which I wonder if that's why this conversation is coming up. I may get a couple since it'll cost me nothing.

Laundry to landscape is legal without a permit in LA county. I went to a free workshop to learn how to do it, and have my system mostly setup, but not running yet. The parts weren't cheap (it ended up being maybe $100), but it's going to take like 1/4 of my front yard completely off the sprinkler system.

Out of curiosity, what parts were required?  My washer just has a tube that drains into a hole in the wall, so I could pretty easily stick it out the window instead and have it water some plants.  Seriously, though, I do laundry like 1-2 times per month.

Wonder if the same can be done with dishwasher?  I could easily just have it drain from a hole in my kitchen wall to the plants outside.  All detergents are phosphate free now, but not sure what else is in there.

[Spondulix]

Out of curiosity, what parts were required?  My washer just has a tube that drains into a hole in the wall, so I could pretty easily stick it out the window instead and have it water some plants.  Seriously, though, I do laundry like 1-2 times per month.

Wonder if the same can be done with dishwasher?  I could easily just have it drain from a hole in my kitchen wall to the plants outside.  All detergents are phosphate free now, but not sure what else is in there.

Here's a diagram with parts: http://dailyacts.org/sites/default/files/L2L%20Diagram%20with%20labeled%20parts.pdf
Some people do just stick a hose out their window and do it that way, but you have to be careful not to go uphill or have too long of a run or it can damage your pump.

Check out #16 about the dishwasher here - not suggested because of the salt in dishwasher detergent: http://greywateraction.org/faqs/greywater-recycling

[deborah]

They also suggest you go for low phosphorus, sodium, boron and chloride laundry detergent. See http://www.savewater.com.au/how-to-save-water/in-the-home/laundry/laundry-detergent-guide

[nereo]

Where in CA do you live?  San Diego only gets about 10 inches of rain PER YEAR -- you wouldn't get much water from rain barrels here.  The laundry grey-water recycling sounds interesting, and of course changing your plantings out to draught-tolerant and native varieties reduces your water needs considerably.

actually, even in areas like San Diego using storage tanks can be effective.  10" of rain is equal to 6.23 gallons of water falling on every square foot of roof.  That means on a typical roof of 1,500ft3 you can collect over 9,000 gallons of water from just 10" of annual rain.  If you wanted to use that collected rainwater for 6 months of the year you could use 350 gallons/week, or about 70 gallons every single day.

It's a lot of water.  Perhaps not as much as DragonCar's current usage, but more than what most gardens need.

If you could capture it all, yes.  But in CA most of that rain comes down in Jan-March, during which your barrels will be overflowing and you won't need to supplement water at all.  Then, by the end of April your barrels are empty and you have another 6 months before more rain.

My back-of-the-envelope calculation was merely a response to Zette's comment that rain-water collection wouldn't work for areas with seasonal rainfall like San Diego. My point was just to illustrate that 10" of rain is a huge volume of water that could potentially be stored for later use.  I agree that rain barrels would be impractical for your situation - i wasn't the one who recommended them.  Instead (if you want to go the rain-water collection route) I suggest(ed) an above ground cistern... basically rainbarrels on steroids that can hold thousands of gallons instead of just 40-60gallons each.  Re-using large poly tanks from ag farms, or above-ground pools, or doing some basic masonry and lining it are all ways you can store several thousand gallons of water for use later.  It's a common practice for 'off-the-grid' homes, especially in areas with a dry season.

that's all i was sayin'.

[guitar_stitch]

Yeah the first month was 17000 gallons (on automatic) so no dent there.  I'm manually running things now, so not sure what my long term needs will be.  Looking into a system with moisture sensor as my clay soil holds moisture pretty well.  But there's also some kind of leak in the irrigation lines that would need to be resolved which sounds like a major pita

Fix the leak first!  Jesus, 17,000 is a lot of water for a month.  Don't underestimate how much that leak is costing you. 

[dragoncar]

Yeah the first month was 17000 gallons (on automatic) so no dent there.  I'm manually running things now, so not sure what my long term needs will be.  Looking into a system with moisture sensor as my clay soil holds moisture pretty well.  But there's also some kind of leak in the irrigation lines that would need to be resolved which sounds like a major pita

Fix the leak first!  Jesus, 17,000 is a lot of water for a month.  Don't underestimate how much that leak is costing you.

I now use the manual shutoff valve to irrigation lines and only open it before running a program, then shut if off again.  The leak costs me, but finding the leak won't necessarily be cheap, either

[TrMama]

Finding the leak isn't necessarily difficult either. My dad spent his summer reworking the irrigation system of the townhouse complex he lives in. He found tons of leaks just by looking for areas of ground that were wetter than they should have been. Don't run the sprinklers for a few days, but leave the main valve open. Then walk around and look for wet spots. When you find one get your shovel out and start digging. You won't have to dig very deeply. I believe nearly all the leaks he found were the result of joins not being properly tightened when the system was installed 10 years ago.

[guitar_stitch]

I now use the manual shutoff valve to irrigation lines and only open it before running a program, then shut if off again.  The leak costs me, but finding the leak won't necessarily be cheap, either

Finding the leak should be free.  This is the DIY category, after all.  ;)

[jamal utah]

Pumping out of a storm drain?  WTF?

1.  Very illegal.  Everywhere in the US, anyway.

2.  Very unhealthy.  Stormwater is every city's biggest pollution problem.  Please don't put it on your yard.

3.  Very ridiculous.  You're worried about your water bill, but your first thought is theft rather than conservation?  Grow up.

Duuuuude.... I don't know if it's illegal here.  But I do know that stormwater runs directly to the bay (so says the "no dumping" sign on my curb), or in nearby cities to the water processing plant (which overflows raw sewage into the bay during heavy rains).  Most municipalities are installing bioswales to reduce the amount of water entering the stormwater system.  So I see no moral issue with using the water.   If anything, this seems beneficial for everyone involved (unless the polluted water kills my plants?).  So grow up yerself!

Yes, it may kill your plants. If it is off the street it will have oil and petrol mixed in it, and if it is off some people's roofs it may have some chemicals in it that plants dont like. Bio-swales and rain gardens usually include specific plants that grow better than others in polluted environments - depending upon the pollutant expected in the bio-swale. If you take what's in the drain, everything will be mixed, and you probably have no idea of the pollutants involved and you certainly don't want to put it on your vegetables in case it includes feces or heavy metals. You may end up polluting your soil. People who have their block of land innundated by floods often need to get their block of land fixed because it has been polluted.

+1 Environmental engineer here. I wouldn't recommend pumping out of a storm drain. It's hard to say what you may find in that water. While the intent of storm drains is to only capture rainwater, these systems often capture a lot of other nasty stuff. People also illegally connect to these systems to dump all kinds of crap. The fact that you are seeing water in the drain even when it hasn't rained is telling of this.