View Full Version : Hot Water line to toilets

07-16-2006, 04:44 PM
Hi everyone,
Just starting new house construction, and want to run hot water lines to the toilets, to prevent condensation. Can't seem to find any discussions on this topic. System is a well water operation. Good idea or not ? Why or why not? Thanks in advance for any thoughts.

Gary Swart
07-16-2006, 05:05 PM
Not a good idea. As I understand it, the hot water can break the toilet. You might be able to use a tempering valve that would mix hot and cold water to give an acceptable temperature, but don't run straight hot into it.

07-17-2006, 06:01 PM
Thanks for your input. I thought this question would generate a significant number of responses.

07-18-2006, 06:05 AM
I thought about that once as a water conservation measure, thinking that instead of running the not-yet-hot water in the shower, I'd use the toilet first, flush with not-yet-hot water, and then have hot water ready in the shower. Of course that only made sense if I was going to use the shower immediately, so I abandoned that idea and bought a Chilipepper appliance (http://www.chilipepperapp.com/), which works pretty well.

Anyway, absent a full-time hot-water circulating system, I doubt it'd be hot enough to break the toilet, at least on the first flush. Gary's suggestion of a tempering valve is probably the best bet. I inadvertantly solved this problem when I re-plumbed my house overhead, following an under-slab leak. The cold water line winds up being attic temperature (i.e., very warm) -- ain't nothing going to condense on that toilet.

07-18-2006, 06:17 AM
There's another thread discussing sweaty toilets here -- I suggested on that one you just buy a submersible aquarium heater and use it to keep the tank at a cozy temperature. You could really go nuts and build a controller that would determine the minimum temperature required to keep the tank exterior above the dewpoint and power the heater appropriately. It'd be a good science project, or a good gift for your girlfriend ;) .


07-18-2006, 09:11 AM
hi wiz boy

I agree with you. It stuns me that this topic has never been discussed in detail and that it is not "standard" practice everywhere to plan for a way to let cold pipes get warmer in the house first before you flush the toilet with it.

i just posted on the other thread. I think it is

i have often thought about how to run plumbing pipes so as to get the water moving through the whole house and then tap into that for the toilet supply. The idea is to use water that has already given up its coolness and picked up warmth, a little bit of "natural" hydronic heat transfer just to flush the toilet. Makes no sense to me to have extremely cold water for the toilet or the lavatory sink. Or anywhere else.


master plumber mark
07-20-2006, 10:04 AM
If you were to run hot water to your toilet

two things will happen to you

the wax ring will eventually "melt away" that forms the seal
to the flor

the toilet tank could very easily just suddenly go SNAP

one morning.... remember that you will have normal

room temp water in the toilettank first thing in the morning....

then you flush it and throw in hot water into the china tank....

thats not good at all...

china does not like to be put through srtess like that..

07-20-2006, 11:39 AM
Another concern I might have is the growth of unhealthy molds and other smelly yucky stuff in your tank. A toilet tank isn't air-tight like a hot water tank, so it will get a little "swampy' in there.

07-20-2006, 12:58 PM
Oooh, excellent point. Now we have to add a chlorine injector to the mix...

07-20-2006, 02:32 PM
You don't want chlorine, at least in higher than drinkable levels, in anywhere there are plastic or rubber parts...it usually will turn them to mush quickly.