Anti-Sweat valve for toilet?

[kharrisma]

Hi Forum Folke,

Like lots of others, I have a toilet that sweats practically all year 'round, even in Winter. I'd like to add an anti-sweat valve to the fill plumbing, but I frankly don't see how it could possibly work as a "drop-in," without some creative plumbing.

The toilet is easily 20 feet from the water heater (that's not counting the vertical rise). At the time of flush, the hot water pipe going to the valve is going to be full of cold water (having cooled in the basement over time). This is a 1.6 gallon flush toilet... I don't see the hot water ever even reaching the toilet by the time the fill valve closes, and even if it did, there wouldn't be much of it. You know how long you have to let the water run before you actually get HOT water from the tap!

Is there any way around this? I have this half-developed idea bouncing around involving a constantly recirculating loop, using a small pump at the water heater to circulate hot water through this loop, which the anti-sweat valve would be connected to by a very short stub. If I'm thinking clearly here, just the water from stub, through the hot port, and to the mix port of the valve would be cold (probably not even a cupful); just a second of flow and the hot water would be right there on demand, no waiting. I'm having some trouble visualizing how this would have to be plumbed into the existing plumbing, though. I'm picturing a pump teed off of the hot water output, piped to the location of the valve, two 90 ells (where the tee and stub actually feeding the valve would tap off from), and back to the water heater... but where would the return water go? The cold water feed to the heater? Would I need a check-valve in the "return from anti-sweat-valve" run to prevent cold water from flowing "wrong way" into the loop?

I think the concept is good, but I'm not familiar enough with the available hardware (or what it's properly called so I can ask for one) to figure this out on my own. Once the hard part of designing the circuit is done, the actual mechanics of installing the stuff should be a cinch... God knows I've done enough cutting/cleaning/sweating of tubing over the years, so far (knock wood) without leaks.

And even if it could be made to work, I'm not sure it's even economically feasible to do so... the pump would have to be always running (or have some sort of thermal sensor to know when to turn on and off, or be on a timer or something), and maybe the cost of running this thing, the extra time the heating elements in the heater would have to run, pulling more current from the electrical system, bigger monthly electric bill... I just dunno. Advice from far wiser heads than mine seems to be needed here. Appreciate your taking the time to read (and attempt to make sense of) this, and any ideas you may have.

 

[TomFOhio]

There are a couple things you could do. They make liners that glue in the tank that will help with condensation. Also
you can buy a mixing valve where you hook the hot and cold into it and then you can mix the water to the toile the temp that
you want. Here is picture of one.

 

[kharrisma]

Hi TomFOhio,

Thanks for taking the time to slog through that long-ish post and reply!

I've researched the liners... prevailing opinion seems to be that they don't really work very well. Plus, my reservoir cavity is really weirdly-shaped; trying to line this thing completely would be an absolute nightmare. I'd tackle it, if I thought the results would be really good, but it doesn't look like that would be the case.

As far as the mixing valve goes, that's the same thing as an "anti-sweat" valve; mixes hot water with the cold so that "tempered" (lukewarm) water fills the tank. Problem remains the same, though; the "hot" water pipe to the valve will be full of water that has cooled to cellar temperature (fairly cold), all the way from the water heater to the valve itself. By the time the tank has filled (low volume, being a 1.6 gallon-per-flush), the actually hot water would just barely reach the tank. Result: tank full of cold water, hot water pipe purged of cold water and now full of hot water, but none of that hot water into the tank. Now that hot water in the pipes will begin cooling, and by the time another flush is required, it'll be cold again. Hot water never reaches the tank, unless there are consecutive flushes (as in the AM when everyone is using the bathroom). Rest of the time, it's the same old tankful of cold water, sweating and dripping all over the floor.

The whole concept of a mixing or "anti-sweat" valve is a good one, but it overlooks the reality of the hot water in the pipes cooling off to ambient between flushes, and having to run all that cold water out of the pipe (into the tank) and the actually hot water never (or barely) reaching the tank. It probably worked pretty well when the old-school toilets used like 5 gallons of water per flush; plenty of time/volume for the hot water to reach the tank. If a more modern, low-volume-flush toilet is really close to the water heater, it might work fairly well, but if it's any distance away, it'll never see any actually hot water. Kind of a problem, if the whole purpose of the thing is to mix hot with cold to get warm... no hot = cold.

 

[TomFOhio]

I see where your coming from and the problem you have. You could run a return line from your water heater to the
hot line going to the toilet. You could look on-line to see how its done. There's many houses that have return lines to
the faucets so the hot water is there when they turn them on.