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What is a shower valve and how do I replace it?

Shower valveLet’s take a look into some of the usually unseen parts of a great shower. In this post we’re going to look at the shower valve and why you might replace it.

Maybe you’ve heard your friend or a plumber talk about a leaking shower valve or that one was required when building a new shower. Ever wondered what the heck are they actually talking about?

When people are talking about a ‘shower valve’ they are usually talking about one of the following;

  • a pressure balancing valve

  • a thermostatic valve / thermostatic mixing valve

  • a diverter valve or a transfer valve

Pressure balancing valves and thermostatic valves are involved in controlling and maintaining the water temperature of your shower. While diverter valves and transfer valves are involved in directing or re-directing the flow of your shower water from the shower head to the tub faucet (or to the hand-held shower head, etc).

Pressure-balancing valve

The most common type of temperature control valves in the household shower. The valve maintains shower temperature by ensuring that the ratio of hot water to cold water stays constant. The valve (more info) utilizes a piston or diaphragm with ball-bearings that responds to changes in the pressure of the hot and cold water pipes. Even when pressure fluctuates, say when the toilet is flushed, the valve will restrict the flow of hot water so you don’t suddenly get scalded in the shower. Instead, the cold water is a reduced as well so overall pressure is lowered, but your shower water temperature remains the same.

Thermostatic mixing valve

This valve acts to control the water temperature specifically and to a pre-set temperature. The big advantage of the valve is that you can turn the shower on and simply wait for the shower water to reach your desired and pre-set temperature. No more fiddling around with the shower taps, acting like a bank robber trying to crack a bank safe!

Thermostatic valves can come in digital electronic form or in the more common manual form. The manual form uses a heat-sensitive material, usually wax, which expands with heat and restricts the flow of hot water. In an automatic balancing act, as less hot water gets through, the temperature reduces and the wax cools and shrinks letting more hot water through. This balancing act gives you a steady temperature controlled shower.

Diverter & transfer valve

As mentioned above, diverter and transfer valves change the flow of your shower water. Diverter valves only divert water in one direction. So with a diverter you can run water from either the shower head or the bath faucet for example. With a transfer valve, you can run water from multiple outlets. Some hand-held showers or shower panels will use a transfer valve to run water from both the fixed shower head and the hand held head or horizontal sprayers.

Why change or replace your shower valve?

  • It leaks. Obvious right? You should replace a leaking shower valve as soon as possible as it might be leaking more behind the wall where you can’t see. This could do a lot of water damage to your bathroom walls.

  • It’s slow to react. Your shower used to be great. Now every time someone turns on another tap in the house whilst you’re showering you shriek in terror! Suddenly scalding hot then the next moment chillingly cold, it’s time to change or upgrade your shower valve.

  • You want the benefits of a pre-set automatic temperature. Having a preset and controlled temperature can save you time and hassle fiddling around with water temperature. Also, having a preset shower temperature can be a good safeguard for young children and the elderly.

A selection of popular shower valves


Delta R11000 3/6 Setting Diverter Rough
Diverter Valve$$3.8

Moen 3510 IPS Pressure-Balancing Valve with Volume Control
Pressure Balancing Valve$$$4.4
KOHLER Rite-Temp Pressure Balancing ValvePressure Balancing Valve$$4.2

Moen 2510 PosiTemp 1/2-Inch IPS ValvePressure Balancing & Temperature Valve$$3.9
Moen 2570 Posi-Temp Pressure Balancing Cycling ValvePressure Balancing & Temperature Valve$$4.2

Moen S3600 3/4-Inch ExactTemp Volume Control ValveTemperature Control Valve$$5.0

Problems with shower valves

  • Lime build up. Lime and dirt can build up over time in the shower valve causing problems like hot/cold temperature changes.

  • Wear and tear. As shower valves age and suffer wear from everyday use, eventually you’ll get some problems that need a repair. Valve seals may eventually fail and start to leak water. Also as ball bearings wear, the reaction speed of pressure and thermostatic valves may slow. This means your shower temperature might start to fluctuate wildly as your valve becomes too slow to react to sudden changes in water pressure.

  • Hot water service change. If you change the temperature of your hot water service or the unit entirely, this might cause problems. You might need to adjust the stop in your pressure balancing valve or the temperature setting in your thermostatic valve to accommodate any change.

Fixing problems with shower valves

  • Clean it. Remove the cartridge and anything else that is simple to disassemble and soak in CLR or other lime remover product (check CLR is safe to use, it might damage some plastics – try white vinegar for plastics). Lubricate with silicone grease and reassemble.

  • Replace it. Not totally simple, but should fix any issues. You’ve probably had the valve for a very long time, it’s time to install a new one.

How to change or replace a shower valve

If you need to repair a shower valve or are looking to upgrade to a thermostatic one you’ll need some quite good DIY know how. Replacing a shower valve is a lot more work than replacing a shower head as you need to get into, cut and refix plumbing pipework.

As a broad overview here are the steps you’ll need to tackle;

  • shutting off the water

  • remove shower mixer trim and handle

  • remove caulking and trim plate

  • cutting a larger access hole

  • disconnecting pipe fittings – both threaded screw and soldered that’ll require cutting

  • cutting out the old valve

  • cleaning and sanding new copper pipe

  • soldering copper pipe

  • disassembling plastic parts from your new shower valve before soldering

  • reassembling plastic parts from your new valve after soldering

  • maneuvering the valve within the wall cavity

  • testing for leaks & fixing leaks

For a detailed how-to guide, we like about.com’s plumbing guide here: http://plumbing.about.com/od/shower_and_tub/ss/Replace-A-Shower-Valve.htm

If you don’t have basic plumbing equipment, good to advanced DIY skills or the time, we’d recommend getting a plumber in. A plumber will be able to fit your new valve quickly, test for leaks for you and give you peace of mind.

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