Hopefully someone out there has this problem too. One of my showers
has this insane problem of changing water pressure and water
temperature when someone else is in the other shower in my house. The
pressure starts out OK, but then once someone else gets in the other
one, the water either gets insanely hot for a few seconds or turns
cold/luke warm for a longer time and the water pressure drops. My dad
has tried to figure it out and can't at all. He's asked around at Home
Depot and Lowes and no one seems to know. So if anyone out there has
any ideas, I'll be glad to pass them along to him.
This is very common. You have one pipe feeding the house. It is split into
two in the house, on for hot, the other for cold. A given size pipe can
supply a certain amount of water. When two faucets are opened, the pressure
will drop some in the system and neither gets full pressure. Depending on
whether the hot or cold is opened on the second faucet, that will increase
or decrease the temperature coming out of the mix on the other faucet.
To (partially) solve the temperature problem, install a temperature sensing
shower control. There are two types, one is an anti scald, the other is a
temperature control. The anti-scald will prevent the water from exceeding
the temperature the user has set while showering. If another faucet is
opened, the flow may drop a bit, but you won't get burned. The down side is
that if the other person turns on the hot water, you will get less and you
can get a chill. (I have this in my house)
More expensive temperature control units will compensate for either hot or
Another part of the problem is the amount of water and pressure available to
you from the main. If it is an older house, chances are the water fed is
3/4" rather than the larger 1" commonly used today. No matter what fixes
you do in the house, only so much water can pass though the pipes. If you
don't already have them, low flow shower heads will help also. One of the
best for the money is Saver Shower (do a Google search) as they still feel
good with reduced flow.
Other factors are the incoming water temperature, the setting of the hot
water, size of tubing at the showers. They won't fix the problem, just
change the degree of it. You can't change the temperature the water comes
in from the street or well.
As you stated, setting of the hot water heater too high can cause some
of this, especially when flushing a toilet while someone is taking a
shower. If the temperature is set too high, it takes a lot more cold
water to make it comfortable for a shower. So when another cold water
faucet is turned on, the hot water immediately becomes too hot. Keep
the water heater down around 120F like they recommend.
Install larger 1 inch water lines thruout, beginning at the meter. If
the outside supply line is less than a inch it should be replaced too:(
Change to ALL BALL VALVES, they have essentially no restriction and
that helps flow a lot. Plus they never go bad....
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