I assume, but am not sure, that this is caused by someone else in the house competing with the shower for cold water.

I'm guessing an anti-scald valve might be necessary but perhaps there is a way to keep the cold water pressure higher so that it doesn't drop as much when someone flushes a toilet or something. The shower in question is on the 3rd floor.

Added: I have since learned of at least three approaches. 1) pressure balanced valve 2) thermostatic mixing 3) anti-scald shower head

Here is a good site comparing the first two: http://www.hometips.com/buying-guides/shower-valve-anti-scald.html

The anti-scald showerheads I have found online are very inexpensive (under $30) but poorly reviewed.

1 Answer 1


Adjusting the whole-house water pressure is unlikely to solve this problem, simply because you set your shower temperature based on some initial balance of hot and cold. When other people draw cold water only, the pressure difference will still have the potential to affect your shower temperature.

Instead, you should get a pressure balanced valve or shower fixture. These fixtures automatically reduce hot water pressure when cold pressure falls, so instead of a temperature spike you simply get a momentary decrease in output pressure. You can find pressure-balanced fixtures (which would replace your existing shower fixtures) or an independent pressure balancing valve (which you'd want to install near the shower but would allow you to keep your existing fixture).

  • Manifolds can be used to provide balanced pressure throughout the entire system, though installing a manifold in an existing (trunk and branch system) would be costly. For new builds a manifold systems can be a good choice, though can cost more since it typically requires home runs for each fixture.
    – Tester101
    Feb 4, 2012 at 17:50
  • I wonder... if you replaced the existing system and added a manifold, would you still be required by code to install pressure-balanced shower fixtures? Feb 5, 2012 at 1:03
  • Thermostatic mixing valves seem related, is there a reason to prefer that over pressure balanced valves? Feb 7, 2012 at 22:17
  • Michael: After looking at some thermostatic shower valves, I gather they are perhaps more precise than just pressure balanced ones, but possibly also more expensive. The only thing I can say for sure is that if you are not replacing your existing shower valve, you cannot just install a thermostatic valve upstream to solve the original poster's problem; a thermostatic valve would have to be in the fixture you use to set your shower temperature, or else you'd be stuck maxing out at whatever temperature the thermo-valve was set for. Feb 9, 2012 at 4:13

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