Author Topic: Insulating copper pipes coming out of hot water tank  (Read 563 times)

Case

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Insulating copper pipes coming out of hot water tank
« on: December 10, 2018, 07:53:06 AM »
I am looking to insulate the pipes that come directly out of my hot water tank.  These are generally known to be sources of heat loss due to the hot water in the tank rising out of them.  However, they are located next to the flue, and it is often noted to not use PEX insulation it is not stable at higher temperatures.  Therefore I was thinking to get some fiberglass insulation sleeves for these but was curious what other people have used.

I also saw a comment in my previous post related to this that the code might not allow insulating that thing in my area... anyone else ever encountered this?

Jon Bon

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Re: Insulating copper pipes coming out of hot water tank
« Reply #1 on: December 10, 2018, 11:36:42 AM »
Well you have a power vent tank with a PVC exhaust correct? So you are probably fine to insulate. If you can touch the flue with your hand while it is running and the insulation does not directly contact the flue I would think you are fine. An old 80% 150k btu furnace I would not recommend, those pipes get HOT, but a HE 50k btu hot water tank is probably fine.

However.

You are not going to save any money or really get any benefit from it, but go crazy if that is what you want!

sol

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Re: Insulating copper pipes coming out of hot water tank
« Reply #2 on: December 10, 2018, 11:53:53 AM »
Regular old foam pipe insulation will work fine.  It doesn't burn, even if it gets too hot. 

Plastic venting means you have a high efficiency gas furnace, so it won't even get hot.  On the other hand, by virtue of having a big old chimney in the middle of your water heater you're efficiency is never going to be very high as you're sending heat up the pipe.  Electric water heaters are essentially 100% efficient through resistive heating, but they cost more to operate because electricity costs more per unit energy than does natural gas.  Most people are really worried about their costs, not about efficiency.

I just replaced a water heater last week, then had a professional replace it again after the theropile failed under warranty.  He said a couple of useful things I hadn't considered, including that pipe insulation is generally a tiny tiny improvement.  You probably won't recover your $5 in insulation costs over the life of the water heater.  Other tidbits I picked up.

1.  My TP line was pvc, but not the kind rated for 210 degrees, and had to be replaced.
2.  My expansion tank was full of water, because the bladder had ruptured.  He said they charge $175 to replace it, but I bought one at Home Depot for $37 and it literally just screws on after you pump it up.
3.  Those water feed lines have gaskets at the junction with the water heater, and so don't require teflon tape.
4.  One of the gas line feeds is a flange fitting without any gasket that still doesn't require thread dope.  He said amateurs always put that stuff on every gas connection point, which is one of the ways that pros can tell whether the install was done by another pro or not.

Case

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Re: Insulating copper pipes coming out of hot water tank
« Reply #3 on: December 10, 2018, 01:23:34 PM »
Regular old foam pipe insulation will work fine.  It doesn't burn, even if it gets too hot. 

Plastic venting means you have a high efficiency gas furnace, so it won't even get hot.  On the other hand, by virtue of having a big old chimney in the middle of your water heater you're efficiency is never going to be very high as you're sending heat up the pipe.  Electric water heaters are essentially 100% efficient through resistive heating, but they cost more to operate because electricity costs more per unit energy than does natural gas.  Most people are really worried about their costs, not about efficiency.

I just replaced a water heater last week, then had a professional replace it again after the theropile failed under warranty.  He said a couple of useful things I hadn't considered, including that pipe insulation is generally a tiny tiny improvement.  You probably won't recover your $5 in insulation costs over the life of the water heater.  Other tidbits I picked up.

1.  My TP line was pvc, but not the kind rated for 210 degrees, and had to be replaced.
2.  My expansion tank was full of water, because the bladder had ruptured.  He said they charge $175 to replace it, but I bought one at Home Depot for $37 and it literally just screws on after you pump it up.
3.  Those water feed lines have gaskets at the junction with the water heater, and so don't require teflon tape.
4.  One of the gas line feeds is a flange fitting without any gasket that still doesn't require thread dope.  He said amateurs always put that stuff on every gas connection point, which is one of the ways that pros can tell whether the install was done by another pro or not.

Thanks, I'll insulate that thing.

I'm more concerned about the costs, but fortunately the efficiency and cost are related to each other.

I installed foam polyethylene insulation around the hot water pipes this weekend (and will continue to the other places I missed).  The cost was about $8.  Not sure if it will ever pay for itself, but I could tell that my shower this morning was slightly hotter (at approximately the same twisting of the handle as usual).  The shower also heated up a little more quickly.  But yea, hot water is actually pretty cheap.

sol

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Re: Insulating copper pipes coming out of hot water tank
« Reply #4 on: December 10, 2018, 01:38:39 PM »
At least in my house, I think most of the waste in our water heater goes towards heating up the pipes.  I often wait for more than a minute for hot water to arrive at the shower in the master bath, which is farthest from the water heater.  That's many many feet of cold copper pipe sucking the heat out of our water on the way to the shower head, and with that in mind I think we can get the most efficiency (and tiny cost) improvement by taking all of our morning showers consecutively, rather than six hours apart.  It probably pays to get those pipes hot only once per day.

Homes are not terribly efficiently designed, IMO.  In the winters I pay to keep my fridge cold inside of a room that I pay to keep warm, and then I pay to keep my gas water heater hot inside of a cold garage.  Does this all seem terribly backwards to anyone else? 

Case

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Re: Insulating copper pipes coming out of hot water tank
« Reply #5 on: December 10, 2018, 03:48:40 PM »
At least in my house, I think most of the waste in our water heater goes towards heating up the pipes.  I often wait for more than a minute for hot water to arrive at the shower in the master bath, which is farthest from the water heater.  That's many many feet of cold copper pipe sucking the heat out of our water on the way to the shower head, and with that in mind I think we can get the most efficiency (and tiny cost) improvement by taking all of our morning showers consecutively, rather than six hours apart.  It probably pays to get those pipes hot only once per day.

Homes are not terribly efficiently designed, IMO.  In the winters I pay to keep my fridge cold inside of a room that I pay to keep warm, and then I pay to keep my gas water heater hot inside of a cold garage.  Does this all seem terribly backwards to anyone else?

I have had some of these thoughts as well (sometimes to my wife's terror).  It would make more sense to have the water tank located centrally, with bathrooms/kitchen nearby.  I can't think of many downside to this, other than finding a way to make the overall house architecture work/fit (probably not too hard) and possibly making it easier for other people to hear you taking a loud crap (e.g. bathrooms close to kitchen).

If you had a chest freezer, you could store it in the garage (or maybe even outside under an eaves) during the winter, and then move it to the basement during the summer.

The harder part I have reconciling is how to get away from the boring box house.  From a energy/temperature conservation standpoint, a smaller compact house I think cannot be beat.  But, I find myself preferring ranches, which tend to wide/long and with more effective surface area from which to lose heat.


zolotiyeruki

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Re: Insulating copper pipes coming out of hot water tank
« Reply #6 on: December 11, 2018, 12:49:54 PM »
At least in my house, I think most of the waste in our water heater goes towards heating up the pipes.  I often wait for more than a minute for hot water to arrive at the shower in the master bath, which is farthest from the water heater.  That's many many feet of cold copper pipe sucking the heat out of our water on the way to the shower head, and with that in mind I think we can get the most efficiency (and tiny cost) improvement by taking all of our morning showers consecutively, rather than six hours apart.  It probably pays to get those pipes hot only once per day.

Homes are not terribly efficiently designed, IMO.  In the winters I pay to keep my fridge cold inside of a room that I pay to keep warm, and then I pay to keep my gas water heater hot inside of a cold garage.  Does this all seem terribly backwards to anyone else?
Agreed on all counts.  I insulated the hot water pipes in our basement, and noticed a similar effect as Case did--the water coming to the shower was hotter.  My house is like yours--it's a long haul from the water heater to the shower.  The amount of energy radiated by uninsulated copper pipes for the 10-15 minutes I'm in the shower isn't going to add up to much, BUT! it means that I can turn the water a bit cooler, which conserves hot water, which is important when it's Saturday night and there are eight people showering in quick succession.

I have this idea for a kitchen where the fridge fits tightly into an alcove in an exterior wall.  In the winter, you simply open a door or louvers from the alcove to the outside, and the fridge consumes zero energy until springtime.  Like the water heater, however, the savings wouldn't really add up to much.

I'd *love* to see water heaters combined with central A/C, however.  Instead of pumping all that waste heat into the outside, save it to warm up your water!

Prairie Stash

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Re: Insulating copper pipes coming out of hot water tank
« Reply #7 on: December 11, 2018, 06:16:19 PM »
At least in my house, I think most of the waste in our water heater goes towards heating up the pipes.  I often wait for more than a minute for hot water to arrive at the shower in the master bath, which is farthest from the water heater.  That's many many feet of cold copper pipe sucking the heat out of our water on the way to the shower head, and with that in mind I think we can get the most efficiency (and tiny cost) improvement by taking all of our morning showers consecutively, rather than six hours apart.  It probably pays to get those pipes hot only once per day.

Homes are not terribly efficiently designed, IMO.  In the winters I pay to keep my fridge cold inside of a room that I pay to keep warm, and then I pay to keep my gas water heater hot inside of a cold garage.  Does this all seem terribly backwards to anyone else?
Agreed on all counts.  I insulated the hot water pipes in our basement, and noticed a similar effect as Case did--the water coming to the shower was hotter.  My house is like yours--it's a long haul from the water heater to the shower.  The amount of energy radiated by uninsulated copper pipes for the 10-15 minutes I'm in the shower isn't going to add up to much, BUT! it means that I can turn the water a bit cooler, which conserves hot water, which is important when it's Saturday night and there are eight people showering in quick succession.

I have this idea for a kitchen where the fridge fits tightly into an alcove in an exterior wall.  In the winter, you simply open a door or louvers from the alcove to the outside, and the fridge consumes zero energy until springtime.  Like the water heater, however, the savings wouldn't really add up to much.

I'd *love* to see water heaters combined with central A/C, however.  Instead of pumping all that waste heat into the outside, save it to warm up your water!
https://www.homedepot.com/p/Power-Pipe-3-in-x-48-in-Drain-Water-Heat-Recovery-Unit-R3-48/203456041

Most of the heat from hot water is wasted going down the drain. THe heat recovery system heats the water going into the hot water tank, pre-warming the water.

Currently, for myself, this has a very long payback period since gas is incredibly cheap (CMHC link has estimates on savings). Its main benefit is saving the environment.
https://kitchenandbathclassics.com/eco-friendly/advanced-plumbing/drain-water-recovery/

zolotiyeruki

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Re: Insulating copper pipes coming out of hot water tank
« Reply #8 on: December 11, 2018, 08:57:51 PM »
I actually heard about those several years ago. IIRC at the time a 6' length was $600 and rated to recover 50% of the heat.  When I ran the numbers, it was something like a 20-year payback, assuming everyone in our house used the same shower.

Of course, if the alternative is adding a second water heater, or installing a tankless water heater, it may be a reasonable option.

Prairie Stash

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Re: Insulating copper pipes coming out of hot water tank
« Reply #9 on: December 12, 2018, 10:41:00 AM »
The main use of them is for electric water tanks. I went home last night and did some math, my gas is worth $6/GJ and is going up $1 next year due to Canada's Carbon tax plan. My water heater uses about 12-15 GJ of heat/year ($60-90). A 40% reduction could save $24-36/year in my optimistic scenario.

The equivalent amount of electricity is worth about $45/GJ - $540-675. Obviously, electric is a lot more expensive to operate then gas. But a 40% reduction is worth $216-270, a much shorter payback. Electric rates vary, but clearly its a viable way to reduce electric bills, assuming you already heat water wiith electric.

There was one other scenario where it works; the case of someone disconnecting gas and going straight electric. You'll pay more for fuel/electricity/heat but avoid the connection charges - $25/month for me ($300/year). This is only viable for people who have heat pumps already and the gas line is only for hot water. In that case lets say I spend $675 for hot water, subtract the 40% so its $405, subtract the basic connection and I'm down to $100. The numbers are getting pretty close to zero/break even. My insurance will be reduced if I cut off gas, another savings. Electric water heaters are cheaper to buy, that adds up too. We all have differing charges for connections, my numbers won't be the same as yours. I'm not convinced this plan is for everyone, just an interesting thought.

For interest, a GJ of gas emits 50 kg/CO2. A GJ is slightly bigger then a mmBTU, 10 therms to the GJ (its actually 10 therms to 1.05 GJ). Over 20 years this device might save 5 tonnes of CO2 for me. I am unlikely to see government incentives as the cost/tonne saved isn't that great for me, but maybe the policy makers will disagree.