Water temp drops at all faucets/showers?!!

Water pressure set at 65psi at the the house’s regulator valve. At the water heater have an inline pressure gauge - which drops about 6lbs whenever a faucet/lav is opened. Open another same or different floor drops a few pounds more.

Problem: Whenever someone is taking a shower temps drop significantly whenever someone uses a faucet and turns it on to hot or warm. Temps drop at least 10 deg F. Pressure seems to be ok or at most only 5lbs reduced.

House has non auto balanced shower valves - Moen and are 18 years old. Occurs at sinks (temp drop) or other shower/tubs.

Have replaced pressure regulating valve at house and just installed a hot water heater pressure tank at the cold inlet by the H20 heater.

H20 Heater is 18 years old - Rheem. Have 85lbs pressure at house. H20 going bad or could it be something else?

Thanks in advance.

Hi Scott sounds like a flow problem due to either undersized or corroded pipes.
Are the supply pipes Galvinized?
Try going to my article on flow verses pressure at my web site and see if it helps.

Are you seducing non members to your website again???

Come to think of it I should have checked to see if Scott was in Chicago.
Just starting a consumer site, but have a lot of work to do.

Bob do you really wear a hard hat?:mrgreen:

According to OSHA safety rules this is required.
Leave it there.

You said the temp drops 10 degrees? That might be cross-over at old Moen valves. The older valves are known for cross-over if the O ring between the hot and cold is worn. They don’t always drip when this happens, so you don’t know it is happening.


Have seen this with Moen many times single lever valve act as a mixing valve