Water Temp Problem in Shower

[ttthhh]

I've got a strange problem in a new to me house which is has a 15 year old shower. It has a Hansgrohe thermostatic shower valve. The cartridge has been replaced by me, but my problem persists.

Usually, when I turn the water on and direct the water to the shower head, the water temperature isn't real hot. I have to move the temperature control past the button-push-scald-stop and all the way hot and the it is just tolerable.

BUT...the shower also has two seperate controls for two rows of body sprays. If I turn on the body sprays, all of a sudden the water gets hot from all the fixtures. Then, if I turn off the body sprays and just use the shower head it functions normally and I can get it as hot as I want.

The shower is at the opposite end of the house from the hot water heater.

I've also noticed that if I warm up the shower using the shower head only, it takes considerably longer than if I warm it up just using the body sprays.

Thoughts?

 

[GReynolds929]

Do you have a tankless water heater? Has the cartridge been calibrated?

 

[Sponsor]

 

[ttthhh]

Do you have a tankless water heater? Has the cartridge been calibrated?

50 gallon hot water heater.

Another maybe interesting data point...

The house is new to us and I've been working though what needs to be done. I recently got around to the water supply. The existing Honeywell pressure reducing valve was not working. 90 PSI from the city and the pressure dropped to 55 PSI if you flushed a toilet, for example. The shower would run pretty cold if someone flushed a toilet in the house. I replaced the PRV and we're back to 60 PSI and the pressure drop is only 6 PSI now when you flush a toilet, for example. The shower now doesn't run cold if someone flushes a toilet. I also checked out the expansion tank and it was ruptured internally since water came out the Schrader valve. Replaced that as well.

Not right away, but a few days after all that work, the shower was working correctly without having to mess with the body sprays. I thought it was strange to happen not coiencident with some actual thing I did, but I was going to take a win. Then, 10 days later (and currently) it was back to how I described it in the first post.

 

[Jeff H Young]

when you turn body sprays on the gpm volume is much higher allowing more water to flow in less time. so you get hot water faster

 

[ttthhh]

when you turn body sprays on the gpm volume is much higher allowing more water to flow in less time. so you get hot water faster

It can't be this. The shower can run for 10 minutes and not get real hot, but the second I turn on a body spray, the shower head gets as hot as one would expect given where the handle is.

 

[Jeff H Young]

never heard of a shower getting cold when flushing toilet only getting hot . could be something with the shower valve whether its thermastatic or pressure ballancing .
I didnt read well I thought it was taking too long for hot water.