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Water Temp differneces from tub to shower

temperature pressure regulato

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5 replies to this topic

#1 senoiasummer



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Posted 23 September 2013 - 09:19 PM

Hi all,


I'm back for more.  I had a poast below about installing an expansion tank.  Well, I finally got around to installing the tank.  In the process, I learned that my water pressure was ~100PSI.  I measured it at a couple of different places, so I am certain it was accurate.  This explans a copule of on gonig issues I have had including repeated failures of my water valve on my fridge!  In any case, I quickly scampered out and bought a pressure reduction valve and installed it.   Originally, I left it at the preset pressure of 50PSI.  However, after completing the installation my shower was running lukewarm at best.  Does not make for a peaceful DOJO!   I thought maybe I had done something stupid and burned out one of my water heater elements.  I checked them and all ohm out good.  So, I decided to increase the water pressure to 75 PSI.  After I have done that I still wasnt satisfied.  So I took some measurements.  Used a meat thermometer and caught the water in a cup to try and "normalize" measurements from show to tub.  My water heaters (2 50 gal electric, in series) are set to 125.   They are in the basement on the left hand side of the house.  The materbath is on the first floor right above (almost) the heaters.  The kitchen is on the first floor on the Right hand side.  The powder room is first floor middle.   Upstairs there are two bathrooms each with back to back vanities and a tub/shower combo.  All of the tub/showers (including the master) have a single control valve that turns CCW for hot CW for cold.  There is know on top of the tub spiggot that you pull up to divert the water to the shower.  When the shower is running for all 3, there is no water comming out of the tub.


The master measures 116 tub/104 shower.   The upper Left measures 116 tub/106 shower.  The upper right measures 104 tub/100 shower.  THe hottest water is the Upper RH vanity (i.e., fartherest away from the Water Heaters) at 124.  The coolest is the upper RH tub.


So, my questions are, 1) why is my shower not as hot as before I put the pressure regulator in?  2) why is there a 10 deg difference between the tub & shower temp 3) How do I fix this.    I tried to adjust the knob in the downstairs tub/shower, but it is already adjusted as far as it will go in the hot direction.  I guess I could crank up the water heater temp, but really dont want to do that if I dont have to.


What are my choices.



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#2 olyteddy



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Posted 23 September 2013 - 09:44 PM

What are your valves? Is it a separate control for the shower or do you turn the shower on by pulling up on a diverter on the tub spout?

#3 senoiasummer



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Posted 24 September 2013 - 09:28 PM

It's got a diverted that you pull up on the tub spout. The fixtures are Price Pfister.

#4 telefunkenu47



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Posted 29 September 2013 - 07:49 PM

T equals P over V. Id turn my upper thermostat up to 134 or 140, and insulate the hot water lines in the house.

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#5 Bullstok



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Posted 14 October 2013 - 09:21 PM

If water heaters are truly in series it is unuseful to have them set for same temp. The only reason to use series is if one partially preheats from a different source of fuel, or preheats with a different efficiency. But two identical waterheaters should be piped parallel to share the load equally IMHO.

Water pressure does not effect fixture outlet temperature in a significant amount unless your flow is so horrible that you lose a lot of temp by radiating from the lines on the long, slow ass, trip to the fixture. Increased pressure will increase flow and reduced pressure will reduce flow. Volume of water (flow) MAY effect perception of temperature. (getting hit with 10 gallons of coffee would most likely feel hotter than spilling part of a cup in your crotch). Try removing the flow restrictors in the shower heads. (Dont tell the gubment though)

Showers will measure cooler if sprayed into a cup or bucket because of mixing with the air before being measured. Measure directly at shower head for better results.

All shower valves reduce the hot water limit when set correctly. Although not in the same manner of design or the same amount of reduction. Basic shower valves have a limit stop under the handle. It limits how far the knob will turn. Check that first, identical valves should have been set for identical amount of handle rotation. Also recent (last 15 or 20 years) valves are pressure ballanced. Ie: u flush the stool and dont get scalded. What you do get is reduced pressure (flow) of BOTH the hot and cold water until pressure returns. So if there is a blockage on the cold inlet, the hot inlet will be reduced also. With these types of valves, if you turn up the inlet temp (water heater setting), the shower outlet temp will raise the same ammount.

Edit) Ps. Congratulations on the water pressure. Few people have a too high pressure issue. I would call that lucky in a way.

Pps. Pressue, temperature, & volume formulas are not very useful for open systems.

Edited by Bullstok, 14 October 2013 - 09:50 PM.

#6 skintdigit



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Posted 22 October 2013 - 10:09 PM

Bullstock is correct. Pull the shower heads off and check the hot water temperature directly from the shower arm, and remove the handles from your valves and check the scald-control stops for proper settings. Your manufacturer's installation instructions will explain the correct procedure for calibrating these. There is no way that you should be losing 10 degrees of water temperature between the shower valve/tub spigot and the shower arm above. Water heater thermostat settings are not accurate according to the markings on the t-stat. Check your hot temps. at the nearest outlet to the heater, then at the furthest from the heater....make your adjustments to heater thermostats and to faucets between the two locations based on these actual temperature readings. 

Edited by skintdigit, 22 October 2013 - 10:10 PM.

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