Condensation in bathroom after woodstove install

[BC_Josh]

Hi,

I'm not sure which forum I should post this, so I just put this in here.

Since I installed a woodstove, my basement is colder than before, when I ran the gas furnace that blew some heat into the basement through the ducting. Even during a cold snap (not too cold where I am in southeastern BC, Canada, 5F or -15C for no more than a few days to a week typically, and I notice that my basement doesn't get lower than 48F or 9C), so, no risk of freezing water pipes and no condensation issues in my basement.

But, the problem is my toilet "sweats" with condensation, quite badly and it will even pool a little water on the bathroom floor. To remedy this, we don't flush the toilet every time we use it in the winter; if it's "yellow it's mellow" rule, and only flush solid waste down there and that helps a lot. It doesn't do this during the summer or shoulder seasons, so it appears to be the cold air/water coming into the toilet from a colder basement than before that no longer has the heat coming up from the basement below (i.e. too great a temperature difference between the water pipes entering the bathroom and the bathroom room temperature). The water pipe that goes out of the wall, for the toilet, also has a condensation issue and is creating a green dripping pattern on the wall from the copper pipes, which is not good.

Obviously I wish to remedy this situation, and I want the lowest cost, easiest solution, if possible. I could hire an electrician to come and put a baseboard heater into the basement and leave it on low, but that could wind up being very costly over time since the basement walls are mostly uninsulated concrete walls with low R-value, and the rest of the basement is fine. The other solution I have is that when I turn the furnace intake fan on, it sucks some of the warm air next to the woodstove down into the basement, but the intake vent is too close to the woodstove to do this, unless I install a fresh air intake to the woodstove, which I'd like to do eventually but that's a big job and I have other commitments so I'd like to put that off for a year or two.

So, for now, if anyone here could offer any ideas I'd be grateful. I'm thinking maybe a bit of heat tape? That should be cheap to run, right? But, I don't have a ground fault interrupter outlet in the basement to plug it into either.

More insulation around the pipes in the basement?

Get a dehumidifier in the bathroom?

 

[stoveliker]

No good solution from me, but a few thoughts.

Your water coming to the toilet is too cold, leading to the condensation. You could add some (foam) insulation around the water line that also sweats. That'll avoid the green stains, but does create a bigger (uglier?) pipe.

I would be concerned a bit about the water lines that run in your walls. They might sweat too, possibly creating mold in your walls.
Moreover, how well is your air sealing; if not great, the humid air in the home might end up condensing in other places in your walls too (e.g. getting thru outlets in your external walls).

I don't think a dehumidifier in the bathroom will resolve the bathroom issue - at least not completely. If you're taking a shower, I think the humidity will be high enough for condensation on 50 F water lines and toilet (and reservoir) itself regardless of whether a dehumidifier is running.

I think a bigger dehumidifier in the home is needed.
BUT your uninsulated concrete in the basement is going to add a LOT of water to the air in the home; a decent fraction of that will move upstairs from the basement (surely if an open stairs/door connects the two).

The problem in the bathroom could be resolvable with a water line heater.
If you know the relative humidity in the bathroom (or the home as a whole) you can find the dew point, and see what temperature the water should be to avoid condensation. But yes, that'll cost kWh.
If you do that where the main water line enters the home, you avoid any condensation/mold in walls in other places too.

 

[EatenByLimestone]

I’ve seen 2 low cost remedies for this. You used to be able to buy foam kits for inside toilets. I’m not sure if they still offer them.

Next up is a mixing valve. It mixes in some warm water into the cold feed. It’ll keep the tank warm enough not to allow condensation.

 

[EbS-P]

One hotel we were at just ran a hot water line from the Sind to the toilet. After a flush or two it makes a great towel warmer.

 

[begreen]

Maybe insulate the bathroom and putting a small towel heater on a thermostat to keep it drier in there?

 

[BC_Josh]

your uninsulated concrete in the basement is going to add a LOT of water to the air in the home; a decent fraction of that will move upstairs from the basement (surely if an open stairs/door connects the two).

The basement is mostly crawl space, plastic on top of dirt, with a couple of utility rooms I can stand up in (with concrete floors). The hot water tank and furnace with the pilot light on, provides some heat. I should put my thermometer/humidity measurer down there in the winter and see, but it feels dry down there, doesn't smell musty, and there hasn't been any signs of effervescent or mold in the three years I've been using the woodstove upstairs. But, you might be onto something. Thanks.

 

[BC_Josh]

The problem in the bathroom could be resolvable with a water line heater.
If you know the relative humidity in the bathroom (or the home as a whole) you can find the dew point, and see what temperature the water should be to avoid condensation. But yes, that'll cost kWh.
If you do that where the main water line enters the home, you avoid any condensation/mold in walls in other places too.

OK; sound like a good idea. The water I get is from reservoirs that my city collects from creeks fed from snow packed mountains and can be ice cold even in summers. Sounds like the trick would be to get a ground fault interrupter wired in, then use a heat tape on where that water comes into the house, for a good length of the pipe to warm it up some. Thanks.

 

[BC_Josh]

Moreover, how well is your air sealing; if not great, the humid air in the home might end up condensing in other places in your walls too (e.g. getting thru outlets in your external walls).

I should check those this winter, just take the covers off the outlets and pull out some of the outlet boxes to inspect.... but I think those are probably OK, the electrical panel is upstairs and the wires run through insulated walls with vapour barrier (the house was renovated extensively in 1996, with new wiring and insulation).

The windows can get quite a bit of condensation on them in the winter, with the woodstove going. I just take a big sponge and wipe them off in the morning and they are OK in daytime.

 

[stoveliker]

If your flow speed is high, and the length of pipe before it reaches the toilet is long, the warm water may end up cooling down before reaching the toilet. So the length would have to be informed by the layout and volume flowing.
Also, when not using water for a few hours, you'd be wasting energy.
An on demand heater set to very low might be lower usage cost (but a lot more up front).
If your water heater is in a good spot the mixing valve proposed above may be better in the long run.? And if you can do your own plumbing it'll be cheaper.

 

[BC_Josh]

I’ve seen 2 low cost remedies for this. You used to be able to buy foam kits for inside toilets. I’m not sure if they still offer them.

Next up is a mixing valve. It mixes in some warm water into the cold feed. It’ll keep the tank warm enough not to allow condensation.

OK; thanks for the ideas. The toilet already has foam inside the tank. A mixing valve would help if it mixed in warm outside the bathroom before going into the bathroom. I'm concerned about that pipe going through the wall for the toilet (the one that has a tap on it, then a flexible hose feeding the toilet). It's sweating and dripping a bit inside the bathroom, and likely causing issues inside the wall which is a bad thing. That's my main concern.

 

[BC_Josh]

If your flow speed is high, and the length of pipe before it reaches the toilet is long, the warm water may end up cooling down before reaching the toilet. So the length would have to be informed by the layout and volume flowing.
Also, when not using water for a few hours, you'd be wasting energy.
An on demand heater set to very low might be lower usage cost (but a lot more up front).
If your water heater is in a good spot the mixing valve proposed above may be better in the long run.? And if you can do your own plumbing it'll be cheaper.

There is about 15 feet between where the water intake pipe comes into the basement (through the concrete wall) and the pipe that feeds the toilet.

What sort of on demand heater are you thinking of?

The hot water heater is about 15 feet from the toilet.

 

[BC_Josh]

Also, my solution might have to be permanent, since adding the fresh air intake to my stove might not do the job anyway, and I might always need some help to have this issue curbed.

 

[stoveliker]

In 15 ft if water line is only 1/3 gallon of water. You'd need to heat that pretty warm to average out high enough temperature in the toilet reservoir...

So I don't think a pipe heater will work.

The electric on demand "boilers" one can get for a kitchen faucet. But costs more and install needs to be done.

A mixing valve if possible would be my way forward

 

[BC_Josh]

A mixing valve if possible would be my way forward

That seems like the best option. Using anything to do with electricity means having to wire in an outlet nearby and heat tape might not actually work as you've suggested. I only have one outlet in the basement as is, and I'm using it for a freezer and to charge portable tool batteries. However, I would imagine that heat tape on the pipe leading up to the toilet might work if there is some water sitting in it and it got warm enough, but that's doubtful.

A mixing valve would mean that it would be one simple fix, without having to monkey around with electrical (which means hiring someone in my case). I might just do the plumbing myself since I have the tools and I've done it before anyway.

 

[EatenByLimestone]

One other idea crossed my mind and excuse my nerdiness.

Duck feet

Ever see ducks standing around on the ice? Why don’t their feet standing on the ice cool off the rest of their bodies? They employ a tactic called counter current heat exchange in their legs. The warm blood flowing from their bodies flows alongside the cold blood flowing back from their feet. Their cold blood is warmed up a little before it gets back to their body.

I did this when I ran the heating lines for my upstairs through my unheated garage. The lines must pass through my kneewall. I put both lines through a single pvc conduit in the kneewall to protect them, and to also reheat the return line before it jumped into the unheated garage. It’s been working for over a decade fairly well.

Running the cold lines going to the bathroom through a piece of pvc right beside the hot lines will heat the cold lines. Since there’s such a short run and low volume imagine the hot water gets changed out fairly frequently every time you wash hands. Waiting a second for fresh hot water wouldn’t be horrible. The PVC keeps the overall air volume around the pipes small so it heats easily. I use 10 feet of it going through my kneewall.

Google Search

 

[Slimdusty]

Sounds like high humidity in your whole house, you mentioned condensation on windows. Does your bathroom have a fan? I have low humidity in the summers and high humidity in the winter, and battled condensation on the windows while using our wood stove. I bought a dehumidifier and problem solved overnight. What is the humidity level average in your house, not just the bathroom?

 

[bigealta]

Also if you use heat tape you can always put it on a plug in timer to cycle on /off to save some energy.

 

[vatmark]

What is the humidity level in the bathroom?

Sounds like high humidity in your whole house, you mentioned condensation on windows. Does your bathroom have a fan? I have low humidity in the summers and high humidity in the winter, and battled condensation on the windows while using our wood stove. I bought a dehumidifier and problem solved overnight. What is the humidity level average in your house, not just the bathroom?

I was thinking the same thing. Sounds like high humidity in the house.

I find it very interesting that your summers are low humidity. I alway thought of summers being humid but that is all I have known. We get disgustingly high humidity in the summer and low humidity in the winter. We have a dehumidifier running in the summer and a humidifier running in the winter.

 

[Slimdusty]

What is the humidity level in the bathroom?

I was thinking the same thing. Sounds like high humidity in the house.

I find it very interesting that your summers are low humidity. I alway thought of summers being humid but that is all I have known. We get disgustingly high humidity in the summer and low humidity in the winter. We have a dehumidifier running in the summer and a humidifier running in the winter.

The climate here is arid, hot dry summers with relative humidity dipping down to 15-20% on the driest of days. This is a big reason wildfires are so dangerous. Spokane Washington in the news right now. Wintertime we get the moisture be it rain or snow and humidity stays fairly high.

 

[gthomas785]

Your 3 approaches to prevent sweating:

1. Raise incoming water temp somehow
2. Lower indoor humidity somehow
3. Insulate the toilet and supply lines

There are toilets with Styrofoam insulation inside the tank for this purpose. I've also seen retrofit insulation kits but they are difficult to install properly.

My dad had a customer who wanted their toilet hooked up to hot water to prevent sweating. Depending how often you flush the toilet this might not be a bad way to go. However if your hot water line also runs through the basement it may not solve anything since the first bit of water to come up would still be cold. Maybe a small on demand electric heater right by the toilet would work.
If you do go to the trouble of setting up something like that, I would install a crossover or mixing valve so you can switch back to cold in the summer and save some energy.

 

[EatenByLimestone]

The better mixing valves appear to be adjustable.

 

[EbS-P]

The better mixing valves appear to be adjustable.

It your not going to get hot water unless you have a recirculating. . Or you flush a couple times.

 

[gthomas785]

I suppose you could get an aquarium heater and just put it in the tank

 

[EatenByLimestone]

The glass cover might not do well with the sudden influx of cold water.

 

[begreen]

There can be several causes here including a cool, damp bathroom to start with. Here's some ideas to address the issue, many of which have been discussed in this thread.

Toilet Tank Sweating and Condensation: How to Fix | Best Flushing Toilets

A wet, dripping toilet tank is not a plumbing leak. It is condensation, and in most homes it is fully fixable without a plumber. This guide explains exactly

bestflushingtoilets.com

If this was not an issue before installing the wood stove, then just raising the bathroom temp a little may solve the issue. A heated towel rack could do this. Raising the room temp will decrease the relative humidity in the room.