We recently remodeled a bathroom with new shower plumbing with a Grohe
thermostatic valve and body sprays. Additionally we replaced the tub
rough and trim. The problem is that the pressure on the hot water side
drops significantly after about 5 seconds when running either the tub
or shower in hot only. When switching on the cold only the pressure is
great. If the tub or shower is running hot only and we turn on the lav
faucet the hot water only trickles out. This bathroom has a dedicated
40 gal electric water heater located in a closet 10 feet away. One
thing we noticed is that the supply line going into the heater heats
up as hot as the hot water pipe within 10 to 15 seconds. Not sure if
this is part of the pressure problem, but I would think that the
supply line to the heater would only get colder as water flows into
it. You advice is greatly appreciated.
Is the dedicated water heater new or was it there before.
Other than that, I suspect the that it is the thermostatic valve that
protects you from being scalded. It may have been defective. Check with
whoever did the work . I believe Grohe is good stuff.
The water heater was there before. It is the cold water supply to the
heater getting so hot that has me concerned now. It seems that there
is some kind of loop feeding hot water back to the heater after the
hot water runs for 10 to 15 seconds. The cold water supply pipe gets
as hot as the hot water pipe exiting the heater.
Where do you take the cold off for the tank and the tap if at the end
of a line and tee'd you are sucking it outwhen you have the tap turned
on. Or you have your connections crossed not the first to do that.
send picture of set up
The cold should always go to the house then the tank also this
should be no closer than 3 feet from entrance to tank as the
possibility for suck up acures when cold is on . either way without
seeing it this is possible but picture would confirm get a plumber pay
him for a opion and tell him you will fix yourself whats a few bucks.
This is what it sounds like to me have seen it before diy
I think the cold might be going through the thermostatic shower
control and then to the water heater possibly sending hot water back
to the heater. Thanks for the input, I will have an experienced
plumber take a look at it.
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