Hot water gets hotter

Mark Harvey said:

We are on a well and the water comes in, through a pressure system to the water tank. (of course cold is seperate). When taking a shower, the water is cool until the hot kicks in at the showerhead level. The hot is too hot so we turn it down to a comfortable level. After about 90 seconds the water gets hotter once again. Doesn't make sense to me. Can someone explain what might be the cause? Thanks.

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Is it only at the shower? What about the sink next to it, or any other fixture(s) in the house? What kind of shower valve? Moen? Symmons? Kohler?

If this is happening only at that one shower valve, I suspect the stem/cartridge, or "balancing spool" (depending on the make of the valve) needs to be replaced.

If the house has galv or copper piping, you are sending hot water through cold metal pipes at the beginning of your shower. The cold pipes "steal" some the heat, cooling the water (particularly if the pipes are traveling through a cold basement or crawl, and/or if you turn your furnace thermostat down at night).

After a few minutes though, the metal pipes heat up and you get hotter water at your destination.

Ishmael is right, try it at a sink (before you shower, so the pipes are still cold). If it does the same thing there, it's probably the pipes. If the problem does not occur there, it's probably the shower valve.

shower hot water

Thanks, the valve makes sense (MOEN). The plumbing is all PEX and the distance from the tank to the shower is about 15 ft. Almost straight up. I'll try the sink but we don't run the water there too long because we have a holding tank. (rural people know what I'm talking about.)

Mark Harvey said:

Thanks, the valve makes sense (MOEN). The plumbing is all PEX and the distance from the tank to the shower is about 15 ft. Almost straight up. I'll try the sink but we don't run the water there too long because we have a holding tank. (rural people know what I'm talking about.)

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15ft of Pex has almost no thermal mass to speak of. I think it's your shower valve.

There's two basic Moen valves: "Positemp" and "Moentrol". The Positemp has a big, fat cylindrical stem. You turn it on and off by turning the handle. The Moentrol has a smaller cylindical stem that you pull out to turn the water on; push it in to turn the water off, and turn it to adjust the temperature.

If you have the Positemp, you just have to replace that stem. If yours is a Moentrol, then you need to replace the "balancing spool". When you remove the trim plate, you'll see a large screw head next to the stem; that's the balancing spool.

Make sure you shut the water off before you try to work on those valves!

Ishmael said:

Make sure you shut the water off before you try to work on those valves!

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:laughing:

hot water

It must be the Positemp. Thanks for solving this mystery. It isn't a big issue but is baffeling.
Thanks again.:thumbup: