Shower/tub faucet hot water pressure

[korn0140]

I have a question about hot water pressure. I have good water pressure, both hot and cold in my downstairs bathroom. I have good pressure in my upstairs kitchen and upstairs bathroom sink. My shower/ tub on the other hand has good cold water pressure but very very low hot water pressure out both the shower head and the faucet. Any ideas what could be causing this? I don't know much about plumbing, so any suggestions are extremely welcomed.

 

[LLigetfa]

You have a flow restriction somewhere. Modern water heaters have anti-percolation valves that could be sticking, letting through fewer GPM than the tub/shower fixture can draw. The other fixtures probably don't draw enough GPM to be noticeable. Try running several fixtures at once to see if the problem is at the tank.

My wife has a giant soaker tub that has full port valves with no pressure balance spools and when the valve in the HWT sticks, I hear about it.

 

[Sponsor]

 

[korn0140]

Just ran 2 fixtures downstairs and 3 upstairs simultaneously all hot water only. The 2 downstairs seemed just as strong and the 3 upstairs seemed pretty much unchanged. The bath tub faucet remained barely more than a trickle.

 

[LLigetfa]

That appears to rule out the HWT as the culprit. Assuming the shower has a pressure balance spool, that is where I would focus attention.

 

[Terry]

What is the age of the home.
Sometimes older homes have aging galvanized pipes that become restricted.
The hot lines are the first to go, most of the time.

 

[Jadnashua]

Most modern shower/tub valves have a high temp limit adjustment...yours may be set too low, restricting the valve from being able to open the hot water fully. What brand and model is it? Some have a screw adjustment, some a cam, some use a gear that must be removed, and then replaced and there may be other types.

 

[korn0140]

No pressure washer spool, as far as I can see. Correction on the pressure being sufficient throughout the upstairs, my fiancee would not call the hot water pressure in the bathroom sink good enough. Maybe it does have to do with the HWT.

The house was built in the mid 90s, not sure what that means in reference to the pipes.

 

[Terry]

The mid 90's should rule out aging pipes.

 

[korn0140]

Flushed the tank, hoping that sediment build up may have been an issue since it hasn't been done in the 7 years i've owned the house, but no luck. Pressure still low.

 

[Jadnashua]

Modern shower valves normally have two lines of defense: a pressure balance spool valve and a mechanical limit stop. A pressure balance spool valve will normally decrease flow in both hot and cold (while maintaining the balance between them), but will have nothing to do with the limit stop. As I said, this could be your problem. Also, if the valve has service stops, those could be clogged or partially closed. Or, the cartridge itself has a partially clogged passage. But, if the limiter isn't adjusted properly, it can severely limit how much hot water is available.