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Question DetailsAsked on 8/2/2015

My toilet water has been rather warm both in the tank and the bowl

My toilet isn't near a heat source but I've noticed that the tank and bowl water are warm - what is causing this and should I be concerned?

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1 Answer


Most toilets since about the 80's or even 70's have a tempering valve, or a tempering manifold, which mixes hot water with cold to feed the toilets. This puts warm water (should normally be about baby bath warn) into the tank so it is not cold, which causes "sweating" as the cold surface condenses water from the air.

This may be new, or maybe you never noticed it before. Check the incoming water temp flowing into the tank after your flush - if luke warm, all is well. if as hot as full hot on the basin faucet, or what you would call "hot" versus "warm", then either your tempering or mixing valve is letting in too much hot water, or your manifold needs adjusting.

The"manifold" (older method of doing this, though still seen at times in new construction) involves a cold and hot feed, with valves on each pipe or maybe only on the hot pipe, leading into a Tee and then out of the Tee to a third pipe (the blended or "Tempered" water) which then goes to the shutoff valves at each toilet. Adjusting the valve(s) openings on the incoming pipes to the manifold regulates the water temperature - you want to regulate the temp after it has been filling the tank for a bit, not the initial inflow which will be room (or crawlspace or basement) temp water standing in the tempered water pipe.

If you have a tempering valve or mixer valve, looks about like this typically -

may or may not have an adjusting screw on the hot side like that one, or may have a nut to adjust temperature - there are also cheaper ones that are not adjustable. Do NOT unscrew the adjusting screw all the way or you will get a good wetting - most will back all the way out.

Manifold or tempering valve commonly near water heater or in basement or crawlspace right under the bathrooms, though at times (especially in slab-on-grade houses) is sometimes found under the bathroom sink closest to the water heater, then the tempered water line continues on to the other bathrooms from there.

As for worrying - not a significant cause for concern except for the fact that warmer water (but not "hot" will form mold in the toilet tank and bowl faster, waste a bit of energy by using more hot water, and hot water in the tank caused deterioration of seals and gaskets and other rubber and plastic parts - not dramatic unless really quite hot.

If not up to fixing yourself, Plumber can do for about $20-50 parts (if needs replacement rather than adjustment) plus normally minimum service call charge of about $75-150 except up to twice that in a few very high cost urban areas.

Answered 5 years ago by LCD

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