The hot water in my master shower cuts off after about 1-2 minutes. It will come back on about 2-3 minutes later. I have 2 other showers in the house and this is not an issue. It's not an issue with any other faucet (sink, shower, bath, etc.) in the house.

The odd thing is if I turn the hot water on the faucet just to right of the shower, the hot water never cuts off.

I've had 2 plumbers in and they cannot determine what the issue is.

Anything ideas?

Dill-Ag13 said:

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Needs a new valve is my guess

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I've also pulled the valve, and soaked in vinegar to clean it up and reinserted too.

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Needs a new valve is my guess

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That's my guess as well. Neither of the plumbers were willing to replace the value. Albeit they are plumbers sent for the home warranty but that opens up a whole other discussion.

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Do you have a tankless water heater? If so, your hot water flow rate might be below the minimum flow rate for the heater to work. If so, you need to lower the temperature setpoint of the heater.

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Every other shower & sink faucet works fine. I think this would eliminate an issue with the water heater.

PlanoAg98 said:

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Quote:

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Do you have a tankless water heater? If so, your hot water flow rate might be below the minimum flow rate for the heater to work. If so, you need to lower the temperature setpoint of the heater.

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Every other shower & sink faucet works fine. I think this would eliminate an issue with the water heater.

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the initial 'hot water' could be existing water in the lines, and maybe it's insulated better than other fixtures.



I have a similar phenomenon with my newly installed tankless. Turn on a fixture, and you get some warm, almost hot water pretty quickly, but then it's cold, and then the real hot water comes. The initial is simply existing water in the lines, which has a variable temp based on fixture distance and how the well the lines are insulated.

TxAgg07 said:

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I'd start with replacing the cartridge in the valve.

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This. Cartridge is cheap and fairly easy to replace if you have any mechanical acumen whatsoever.

Need more info:
1. New problem or always done that?
2. How far away from the water heater is this shower? How far away are the other showers?
3. Tank or tankless?
4. Pex, PVC, or galvanized pipe?
If Tank:
A. Age of tank?
B. How often do you flush the tank, how long have you had the house?
C. Repiped in the past?
D. Expansion tank installed? (see below)

mefoghorn said:

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Do you have a tankless water heater? If so, your hot water flow rate might be below the minimum flow rate for the heater to work. If so, you need to lower the temperature setpoint of the heater.

Even if you have a tank heater, it might work to lower that temperature setpoint so that you can then turn the shower valve more toward HOT to achieve the desired mixed-water temperature.

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Could also replace the meager GPM shower head that's not drawing enough with something with a little more power

Need more info:

1. New problem or always done that?

New problem

2. How far away from the water heater is this shower? How far away are the other showers?

This shower is across the house from the water heater but there is another shower in the next room equal distance away.

3. Tank or tankless?

tankless

4. Pex, PVC, or galvanized pipe?

pipe

mefoghorn said:

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Do you have a tankless water heater? If so, your hot water flow rate might be below the minimum flow rate for the heater to work. If so, you need to lower the temperature setpoint of the heater.

Even if you have a tank heater, it might work to lower that temperature setpoint so that you can then turn the shower valve more toward HOT to achieve the desired mixed-water temperature.

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The fact that the problem doesn't happen when you run the sink simultaneous with the shower points to the above. There is likely a flow restrictor in your shower head. Remove the flow restrictor and your problem will likely go away.

Any chance there's a thermostatic mixing valve in the loop here?

It may be going bad and causing a problem. If those valves lose sufficient cold water pressure they close completely.

If you have a recirculating pump, check that it is actually pumping in the correct direction. I had this exact problem this year and the idiot plumbers put my original recirculating valve in backwards.

The actual answer to your problem.

You have a tankless water heater. The flow sensor is dirty and not registering when that particular shower is running. You need to disassemble, clean, and reassemble. Google will tell you how. The reason this is only an issue in your master shower is probably lower flow than other fixtures. You could probably pull off the shower head and take off the water saver, then enjoy that pressurized shower you've been missing.

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You could probably pull off the shower head and take off the water saver, then enjoy that pressurized shower you've been missing.

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I replaced the showerhead with a high flow model and that temporarily fixed the issue. I still need to flush the system to clean the filter.