Wife and I are custodians of a house that will be unoccupied and unvisited for probably the next six months or more. We were last in the house three months ago, and I made sure all the sink traps and toilet bowls were full of water then. We visited today, and with the summer heat, the bowl in the upstairs toilet had evaporated completely and was letting sewer gas into the house. I filled the bowl again before leaving, and from a quick Googling, it seems the two leading methods for preventing a toilet bowl from drying out are:
Pour enough mineral oil into the bowl to completely cover the free surface of the water, and
Cover the top of the bowl completely with kitchen plastic wrap.
It seems to me that either of these methods would do pretty well to prevent evaporation from the household side of the trap, but of course they will not be able to do anything to prevent evaporation from the sewer side of the trap. I am guessing that that side of the system is probably pretty high humidity anyway and so evaporation will be pretty low, but of course it will not be zero.
Has anybody had any experience with either of these two methods, and how well they would work to keep a toilet bowl from drying out over a period of many months? Has anyone here tried anything else with good success? We’ll be visiting the house a few times in the coming weeks, so I’ll have a chance to apply whatever solution seems best.
Oil might have an odor that fills the bathroom. The plastic wrap allows the toilet to be flushed but should have a vent hole for that purpose and it should be obvious to someone who wants to use it for its common purposes so it doesn’t appear to be a dorm prank. If no one would care about the odor I’d use the oil, The other thing is to look for a silent leak. Turn off the water supply when you are away and make sure the water level in the bowl doesn’t change over time.
I question the diagnosis that it’s solely evaporation that has caused the lack of water in the toilet bowl. There may be a slow leak. I’d also check that the vents are clear.
To keep a minimum amount of water in the bowl, the most direct solution is an automatic way to add more. For example, something like a water cooler. Put one or more plastic jugs filled with water upside in the toilet bowl. When the water level drops below the mouth of the jug, some air will slip into the jug and release enough water to bring the level up over the mouth again. This will work no matter the root cause of the water loss.
Normally no, as long as there is water in the traps to prevent it. A pressure surge in the sewers could in theory force gas through the traps but proper vents should prevent that from happening.
I agree. I have one bathroom in the house that is almost never used, and I have to flush the toilet every few months to refill the bowl. There’s no way that any substantial amount of water is being lost through evaporation, it has to be a slow internal leak where the water drains away down the drainpipe.
I just thought of another potential solution: plug the toilet. With a plunger or some other removable object. Which I guess is similar to the plastic evaporation barrier, but more liquid-oriented.
I am not sure the answer to the OP, but tangentially, I would suggest shutting off the water supply to the house entirely if the place will be unoccupied for that length of time. If one of the toilet, washing machine, ice maker, water heater, etc. hoses decides to spring a leak, the whole house could be wrecked. We had a toilet hose break overnight while we were home, but it was enough to destroy most of the downstairs flooring. And that was just a few hours - imagine days or weeks of water flowing unchecked thru a house.
100%. I’m managing my mothers house 100 miles away. We have a main shut off for the entire house that is easy to get to (the easy to get too can be a bit of a trick if you’re not a good plumber)
This happened to a friend a couple weeks ago and she was advised that there was a problem with the venting that was causing the water to drain out. I’d ask her more but she’s on vacation.
The trap in any modern toilet is solid porcelain, with no joints in any of the continually wetted surfaces. The only way it could be leaking is if the body of the toilet is cracked, in which case you’ve got bigger issues. Don’t underestimate the power of evaporation! I’ve used salad oil to slow down evaporation, but that got checked about once every six weeks. Plastic wrap with a criss-cross of bright tape should help. I also heartily second the notion of shutting off the main water supply. Will the house be heated? You can get antifreeze that is intended for RV plumbing to add to the various traps so they don’t get split by ice.
Silent leaks are usually a poorly sealed flapper valve in the tank. Water slowly leaks into the bowl and then flows down the drain as the water level in the bowl rises.
Quite right. I lost track of the topic there. Slow leaks can still occur elsewhere. Sometime the wax seal leaks at the flange. A tiny drip can be absorbed by the subflooring or drip below unnoticed. It’s a good idea to check for slow leaks on any toilet once in a while just in case.
Depends on the oil. The advice I saw was pretty specific about using mineral oil (as opposed to vegetable oil). Mineral oil won’t turn rancid or decay. I’m thinking that the kind of oil you rub on a wooden cutting board is the stuff to use here.
The plastic wrap allows the toilet to be flushed but should have a vent hole for that purpose and it should be obvious to someone who wants to use it for its common purposes so it doesn’t appear to be a dorm prank.
A vent hole through the plastic would defeat the purpose, i.e. isolating the bowl water from the atmosphere to block evaporation. We have no expectation that anyone else will visit the house before we return, so I’m not worried about anyone else being weirded out in the interim.
I agree with suggestions to shut off the water main. This is something we do with our own house when we’re going to be away for more than a few days, so I will have to find the main shutoff for this house.
Will the house be heated? You can get antifreeze that is intended for RV plumbing to add to the various traps so they don’t get split by ice.
Thought about this. I was under the impression that standard automotive antifreeze was sewer-safe and could be used for this purpose. Is that not the case?
This perennial problem is actually a crude SOLUTION to the OP question, as it will tend to keep the toilet TRAP full to block sewer gas, at a cost of using water, and pump power, and running up the sewer bill if they charge by water usage…
I think it’s okay. My friends have a cabin in the mountains and in winter, when vacating, they shut off the water main, drain out the pipes, and add around a quarter cup of car antifreeze to the toilet tanks and bowls. The place is on septic, so that may make a difference but I would think not. If there is no risk of freezing then this should not be an issue, of course.
I wouldn’t dump automotive antifreeze in a household drain, there is a reason why it’s supposed to be disposed at the local household hazardous waste drop off site.
RV type antifreeze is sewer/septic safe and designed for plumbing/waste systems. Maybe it would, with the ingredients in it, have a lower evaporation rate than straight water?
If all the water is evaporating through a vent hole in plastic covering the bowl then you probably have a leak somewhere. I suppose it’s possible to be losing water from the other end of the trap also when wind creates low pressure in the vent pipe water vapor in the trap and drain pipes would be drawn away. I’m kind of surprised that just putting the toilet cover down doesn’t prevent the bowl from going dry.
Back to the start of your response, mineral oil makes a lot of sense to stop evaporation and help discover a slow leak. If it was me that’s the first thing I’d try.