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Question DetailsAsked on 1/31/2018

We had to shut off our water outside to fix a leak in the shower. Now the gas water heater only puts out warm water

Water runs out full force but will not get above warm and turning up the heater does not change. You can feel the heat coming out of the vent stack. My husband decided to release all the pressure and still nothing. I do not think it is an airlock because the pressure is good.

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Here are a bunch of previous similar questions with answers which might help:

When you say water comes out full force, I am going to presume you mean full force when only the hot water is turned on. Run down through following list till you hopefully find the problem - otherwise time for a Plumbing contractor (your Search the List category to find well-rated and reviewed vendors to do this type of work).

0) if water is coming out full force when on hot only, not an airlock. An airlock (real rare in household pressurized lines) would shut off the hot flow mostly or entirely.

1) check temperature setting on water heater was not adjusted during the repair for some reason - like to avoid scalding risk when working on the pipes

2) First, check if this is occurring only at the shower (or possibly close by too) or all over the house - if only at/near shower, could be a crossover between hot and cold was inadvertantly created during the repair. Or if a single-handle valve/cartridge was involved, that it was assembled/connected wrong so there is an internal crossover between hot and cold in the valve. For instance, some cartridges can be put in backwards or 180 degree rotation from where they are supposed to go and may totally shut off flow, or allow cross-connection - sometimes even when that faucet is not 'on". Ditto sometimes if internal balls or seals are put in backwards or left out.

3) if the shower faucet was worked on or replaced, exercise it through full range - full hot to full cold - sometimes the initial seating of seals is not complete so it allows cross-flow between hot and cold.

Turn hot water on elsewhere, and listen with your ear at the shower valve for flow through it (not jut the sound of running water in the pipes, but actually at that valve - open it a bit to hear the difference.) If sounds of running water there without any water coming out of the showerhead/tub spout, then likely a cross-connection was created. (Would make noise only when water is running in the house - not in "static" case.)

4) if faucet was changed/rebuilt, check if faucet handle is mounted wrong - may be it is not turning the faucet shaft all the way to the on side.

5) check the temperature on water drained from the bottom drain valve of the tank - if full hot (up to what thermostat shows - typically 125-140 degrees), then problem most likely is where the repair was done.

6) make sure some valve in the house on the hot line was not turned off in the process - though normally that would just restrict the hot flow, which does not appear to be your case

7) rarely, a tempering valve (which provides warm water to the toilets to prevent tank sweating) will go out when the water is turned off and stick open, allowing hot and cold to mix there. Find it (typically looks like this, on line to toilets - may be one for house, or one on each toilet depending on distance of run to them) -

Immediately after flushing toilet, while tank is refilling, check pipes at the tempering valve - one incoming pipe should be full cold, one full hot, the single outgoing pipe to the toilet should be warm. If the incoming "hot" pipe does not get hot then track back on that hot pipe toward the water heater, with hot water continuing to run in sink or tub or such, to see if there is come device which could be causing a cross-connection between hot and cold. (Usually the tempering valve comes off the main hot and cold pipes, which then continue on past it).

8) check water heater for any diagnostic message or "blink-code" on LED's on it. If there is any chance the water in the water heater was partly siphoned out during the repair, it is possible it overheated and a safety sensor shut if off. Check owner's manual on that - sometimes a RESET button has to be pushed, sometimes turned down to PILOT then back up, sometimes has to be shut completely off and sit for number of minutes to cool off, then be restarted from scratch.

Answered 2 years ago by LCD

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