Author Topic: Undersink cabinet - Mold  (Read 967 times)

Frugal Lizard

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Undersink cabinet - Mold
« on: June 22, 2020, 09:02:49 AM »
To the best of my understanding, there are no leaks in the plumbing in the sink cabinet.

The mold is black and grows on the reverse osmosis chambers first and eventually all the inside edges of the cabinet.  It takes about 7 months to go from clean to OMG HOW DID I NOT NOTICE THIS DISGUSTING MESS?

We keep a large bucket for the compost, dish soaps, brushes, spare plastic bags, dish drainer as well as the extra large capacity reverse osmosis tank and three filters. Nothing gets put in there wet-all brushes and dish scrubby stuff stays out until it is dry.

I am wondering if the problem is from of combination of cold or hot water in the copper pipes, the furnace duct comes up 18" from the outside wall and under the cabinet and not right at the outside wall, and the sink above is a massive cast iron baby and there is no ventilation as the holes through the cabinet were filled to prevent mice at some previous time.  The cabinet box itself is really well built to hold up the heavy sink. 

The basement wall below this part of the kitchen has not been insulated yet because there is a whack of incoming water lines, water meter and built-in shelving.  It is one of the last parts of the basement still waiting for insulation but as it is not easy, we hadn't gotten around to it yet. 
The exterior wall above grade is just 2x4 construction with brick and has fiber glass bats that have were state of the art (in 1969). We have a real winter - It frigging snowed in May this year but now it is hot and humid. (yesterday was 88F with relative humidity approaching 78%) Our cold water is from City ground wells so it is lovely and cold.

So all the right conditions to have condensation and grow mold.

I am going to start with:
-covering all the copper pipes with insulated foam wrap to reduce condensation. 
-storing all but the dish soap and dishwasher powder and compost bucket somewhere else.

Any other ideas?
Should we try to get some insulation into the space between the back of the cabinet and the exterior wall to reduce thermal bridging to the exterior?  I am wary of putting a hole in the back of the particle board cabinet.  (the cabinets were made in 1969 by Canac, they are really sturdy still)
Should I be as worried about putting holes in the back of the cabinet to fill the space with loose insulation. 
Should I just try to leave the cabinet doors open at night
Should I mist the area with some bleach every now and then?
Is this problem not fixable and I should just add swabbing the inside of the cabinet to monthly housekeeping chores?

Sibley

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Re: Undersink cabinet - Mold
« Reply #1 on: June 22, 2020, 10:47:33 AM »
Rather than bleach, try one of the mold treatments like concrobium. Bleach doesn't kill spores.

As for storage, I would actually move the compost bucket and plastic bags out. The rest doesn't sound like it would cause an issue, but food scraps sure would and that's what I assume you're putting in there. The plastic bags will have a hard time drying if they get damp at all.

nereo

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Re: Undersink cabinet - Mold
« Reply #2 on: June 22, 2020, 10:53:33 AM »
It does seem like you have perfect conditions for condensation and subsequent mold.  Not just condensation but also the moisture and food from the compost bin.

Are your cabinets designed in a way where you could add a small vent to improve airflow?  Most have an overhanging lip over the toe-kick - you could drill ventalation holes there and they would be completely hidden except when you opened the door - and you could go fancy and cover them with an inset mesh screen using a router.  Or you could just cut a larger hole in the cabinet door and install a vent plate.

Other ideas... you can buy buckets of desiccant (e.g. DampRid®) that helps keep moisture out of enclosed spaces.  Only downside is you have to change it periodically (every few months) and it costs $7-8USD each time.

SunnyDays

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Re: Undersink cabinet - Mold
« Reply #3 on: June 22, 2020, 11:40:34 AM »
Charcoal can also be used to absorb moisture in the air or you could install a battery operated light to increase the temperature and dry it out a bit.

affordablehousing

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Re: Undersink cabinet - Mold
« Reply #4 on: June 22, 2020, 04:16:32 PM »
I don't understand, you keep a bucket of compost in an enclosed cabinet and are surprised it molds? Keep it outside. Seems like a simple fix.

Frugal Lizard

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Re: Undersink cabinet - Mold
« Reply #5 on: June 22, 2020, 05:32:49 PM »
@affordablehousing
The bucket collects the food scraps for about four days and then goes to the compost bin outside to become compost.  The mold is not on the bucket or the tray that the bucket sits on. The bucket gets cleaned regularly (at least once a week).
The mold in the cupboard is black, while compost molds are green or grey and usually fuzzy. 

The garbage drawer doesn't get moldy at all (Yes all the garbage is collected in a sliding drawer thingy with sorting compartments of recycling, landfill waste and organic material that we wouldn't compost at home such as meats, bones and kleenex) This was a very fancy kitchen in 1969. 

@SunnyDays - I have some charcoal for the grill - gonna try a small take away container full.
@nereo - I am going to leave the cupboard door open overnight.  I am also going to put a double bumper on the doors so they sit a little proud of the face of the cupboard.  We didn't reinstall the rubber on the one door that forms a seal with the other door.  It was tatty and gross, unlike the one on the pot drawer that we left on.  (All the double doors had a rubber overlap on the back of the right door that didn't prevent them from closing or pulled the other door open.  It just stops you from being able to see into the cupboard)  There is an air gap but no circulation. 
I have to think further about how to reduce the condensation.  We were having a problem in the basement because the water supply is much colder than air temperature. 
@Sibley - now to find this type of product in the era of COVID. 

I hate having to go out to the compost bin every day and I also hate looking at the ugly bucket so that is why I have this thing in the cupboard.  I am going to try everything else first before giving up my convenient tidy solution.  I think I would rather wipe down the RO once a week than not have a scrap bucket.  If I put a lid on the bucket - that would also keep down the moisture, but then add another step to getting the orange peels...I finally got those kids trained to toss the banana peels without the damn sticker.  A lid might be too much!

Sibley

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Re: Undersink cabinet - Mold
« Reply #6 on: June 22, 2020, 07:16:04 PM »
https://www.homedepot.com/p/Concrobium-32-oz-Mold-Control-025326/100654126

It's widely available, pretty much any hardware store should have it. Good luck.

Papa bear

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Re: Undersink cabinet - Mold
« Reply #7 on: June 22, 2020, 08:34:06 PM »
So you don’t think that adding a bunch of wet food scraps to an enclosed cabinet could add the moisture that would allow mold growth to other surfaces?  I’d start here. 

Then look for other water sources. Maybe your caulk behind your faucet is compromised, letting in a tiny amount of water on a regular basis.  Maybe your disposal has a small leak when you run it.  Who knows.  Look for water first.  The place didn’t have mold for every day of the last 50 years. Something has changed and is adding moisture. 


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lthenderson

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Re: Undersink cabinet - Mold
« Reply #8 on: June 22, 2020, 08:57:48 PM »
I agree with Papa Bear's assessment. Mold needs moisture and I doubt your mold problem has anything to do with the insulation or the lack of ventilation. I would get rid of the compost bucket stored in there as vegetable scraps are mostly water. I would also re-caulk where your counter meets the back splash. From tearing out lots of cabinets over the years, it is really common to see lots of mold on the backsides of the cabinets where the water has leaked through that joint. Also look at the intersection of your faucet to the sink/countertop and also your sink basin to the countertop.

You also mentioned a water filtration system under there. I would check all the joints around that to make sure there aren't any small leaks occurring. For slow leaks that are hard to find under cabinets, I will empty everything out, clean all the pipes really well and put a layer of paper towels underneath that I check often over the course of a day or two with a flashlight for stain marks. Then you just have to work your way up the pipe until you figure out where it is coming from.

What is the humidity level inside your house now? Are you running an air condition that is dehumidifying the air? If not are you running a dehumidifier? The answers to these questions might give some insight to your mold problem.

Frugal Lizard

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Re: Undersink cabinet - Mold
« Reply #9 on: June 23, 2020, 06:41:21 AM »
Thanks @Papa bear and @lthenderson  - on the hunt for moisture sources...

It is really hard to get caulking in the back of the sink, but I should probably refresh - it has been four years since we did it last.

affordablehousing

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Re: Undersink cabinet - Mold
« Reply #10 on: June 25, 2020, 10:43:05 AM »
This reminds me of when I thought I was getting condensation on the ceiling above the shower. I went crazy adding insulation, increasing the size of the bathroom fan, replacing drywall, only to find that there was a tiny pinhole leak in the showerhead connection pointed straight up that was very hard to see.

The lesson I learned is, start with the easy stuff, like taking the OBVIOUS SOURCE OF MOISTURE, your compost, out from under the cabinet. If that doesn't help, then move on to more invasive/difficult interventions.

big_owl

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Re: Undersink cabinet - Mold
« Reply #11 on: June 27, 2020, 07:26:15 AM »
I have a very small compost bucket I leave on my kitchen counter next to the sink with the lid on and empty probably twice a week.  It's used mostly for fruits and vegetables with the occasional eggshells.  Even after 2 or 3 days when I lift the lid it's literally dripping condensation.   All of this condensation is ending up in your cabinet.... No wonder you have mold.  You might as well be storing a bucket of water under there. 

BudgetSlasher

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Re: Undersink cabinet - Mold
« Reply #12 on: June 27, 2020, 10:01:40 AM »
I have a very small compost bucket I leave on my kitchen counter next to the sink with the lid on and empty probably twice a week.  It's used mostly for fruits and vegetables with the occasional eggshells.  Even after 2 or 3 days when I lift the lid it's literally dripping condensation.   All of this condensation is ending up in your cabinet.... No wonder you have mold.  You might as well be storing a bucket of water under there.

Just scrolled down the thread to say something similar.

We too have a compost bin on our counter. And when it is emptied the bottom is often full of fluids; really there is some mold too, but we are not religious about taking it out to the compost pile nor giving it a good cleaning after emptying.

While there may be many things at play, I think the moisture added in a confined space by a compost bucket it probably a big contributor. Unless the compost pail is airtight. The brushes and dish drainer if put away wet could also be adding to humidity issues and mold.

I would move the compost and see what happens.

Alternatively the OP could use something like this (https://www.amazon.com/Under-Counter-Kitchen-Compost-Container-YukChuk/dp/B00BA3LP28/ref=pd_lpo_86_t_1/131-0706590-4386255?_encoding=UTF8&pd_rd_i=B00BA3LP28&pd_rd_r=29d7fc08-e749-4dfb-ad19-f7a7cb48ad8b&pd_rd_w=y2qLR&pd_rd_wg=tRj3U&pf_rd_p=7b36d496-f366-4631-94d3-61b87b52511b&pf_rd_r=5EZ5HZFCKV4DT1NJB0KH&psc=1&refRID=5EZ5HZFCKV4DT1NJB0KH)

We had something like that, if not the same thing, in a prior kitchen, under the sink (throw in many of the OP's circumstances as well, other than year built) and didn't have a mold issue.

big_owl

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Re: Undersink cabinet - Mold
« Reply #13 on: June 27, 2020, 10:39:25 AM »
This thread was very useful for me.  I started googling around and found this:

https://www.google.com/amp/s/yourhomegrownharvest.com/2019/02/23/product-review-foodcycler-fc-30/amp/


I'm buying one of these stat. 

Frugal Lizard

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Re: Undersink cabinet - Mold
« Reply #14 on: June 27, 2020, 05:39:09 PM »
paper towels yielded no obvious leaks
DH spent the afternoon redoing the seal between the sink and the countertop.  It took him over two hours to pick out all the old caulking and rust - yes rust - so I think we know where the water is coming from.  He did a beautiful job.  He has decreed that the sink can't be used until tomorrow morning after 7. 
We have been leaving the door open overnight but we haven't had super humid weather for a couple of days. 
Compost bucket is switched out for a smaller version - so small that it needs to be emptied after dinner.  With all four of us back at home and the garden coming into its own, the compost is being generated really fast.  At the end of the day, when I was too tired to empty it, I put it in the garage. 
There is a little condensation on the water supply line to the reverse osmosis when everyone fills up a water bottle and I make a huge pot of tea - but not enough to grow mold.  I have always had a compost bucket under the sink.  My gramma called it the swill pail (it went into the pig trough).  My mom emptied her bucket in the chicken pen.

It was interesting for me how many people thought putting a bucket for compost under the sink was ridiculous.  I wish we had room for another container in the garbage drawer.  Hopefully the mold was from leaks around the sink and now that is fixed.  And I can return, safely, to my low tech swill bucket.

lthenderson

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Re: Undersink cabinet - Mold
« Reply #15 on: June 27, 2020, 08:05:50 PM »
Sounds like you may have found the problem. When time shows that things are better, you can always go back to the old compost bucket. We found one earlier this year that kind of matched some of our countertop appliances (Stainless) and looked sort of like a wine chilling bucket with a lid. Now we just keep ours on the counter near the sink and dishwasher so everyone is more inclined to use it than tossing stuff in the trash. We empty ours too daily because being accessible, it filled up much faster and it also helps to prevent fruit flies.

affordablehousing

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Re: Undersink cabinet - Mold
« Reply #16 on: June 29, 2020, 12:41:44 PM »
I'm very curious to see how this turns out. I'm still betting on the compost. Older sink cabinets I've seen (built when a carpenter would make the cabinets from plywood to suit a bungalow on site) often had vent holes or a vented scroll pattern on the front. If you've got a standard overmount sink, the caulking is a routine maintenance item so I don't think you did anything unnecessarily. I still would take the compost out.

 

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