Posted by: Fonte Dei Marmi | October 27, 2010

The hidden secret of a great shower: Shower valves.

Okay, we admit it, talking about shower valves is not exactly sexy, but they’re pretty important components so we thought we had better not exclude them.

There are two main types of shower valves:-

Grohe Grohtherm 3000 exposed shower valve

Grohe Grohtherm 3000 exposed shower valve

Exposed valves are wall mounted, usually sticking out by about twelve centimetres. The usual set-up is to have the hot and cold controls at either end of the exposed bar, or to have the temperature controls at one end and flow control or diverter knob at the other. Exposed shower valves are the least popular of the two types, but do tend to be cheaper than their counterparts.  Apart from being quite unsightly they are often used as grab rails which is not a great idea as you can burn yourself if you touch the part where the hot water comes. You can purchase more sophisticated ‘cool touch’ exposed valves where the cold water is sent around the hot water pipe to prevent such an occurrence.

Installation is relatively easy: the valves can be mounted on any wall without the need for a huge hole in the wall.

If something goes wrong it is likely to be one of the knobs, the calibration cartridge or the whole unit.

Hansgrohe iBox universal concealed valve

Hansgrohe iBox universal concealed valve

Concealed valves come in two pieces: the valve, which fits into the wall, and a faceplate (or trimset) that fixes onto it. The faceplate can have more options than are available on exposed valves to allow for multiple outlets, body jets and additional showerheads.  Generally they have one or two knobs or levers; in the case of one, this would normally be a lever and would operate much like a monobloc basin mixer – pull out to increase the flow rate, push in to decrease. Left and right for temperature control. Where there are two controls (usually knobs), one would control the temperature and the other would be flow control and optionally a diverter

Some manufacturers, for example Grohe and Hansgrohe, have “universal” concealed valves. This method allows for any number of trimset styles to be chosen that fit a common valve. Most other manufacturers sell the valve and the trimset as a single product, and they may not be interchangeable. Always check with your supplier as to the best option for your bathroom, and make sure that your installers have experience in fitting the kind that you select.

When it comes to installation, concealed valves cannot be installed in an exterior wall and are most commonly found in airing cupboards or stud partition walls.  The valve should be installed into the shower wall first, the wall tiled and then the faceplate screwed into place.

Concealed valves tend to involve more installation and are more expensive but the overall effect is much neater than an exposed valve.

Hansgrohe "Axor Stark" trimset with diverter

Hansgrohe "Axor Stark" trimset with diverter

With both exposed and concealed shower valves you have the option of manual or thermostatic valves.

Manual valves work in the same way as a standard mixer tap. There is a hot component and a cold component, which you adjust to get the right temperature. Great … until another appliance on the water system is used and deprives the shower of either hot or cold water, leaving you under a stream of either burning or very cold water.

Thermostatic valves have a wax cartridge, which changes shape to let through the right mix of hot and cold water at any time, all of the time. Any changes to the flow of either hot or cold water will not affect the temperature. Whether a digital or knob temperature control you can set it and leave it without having to adjust it if someone flushes a toilet elsewhere in the house. If for any reason the cartridge cannot adjust itself to achieve the desired temperature it will shut off the water.

Here’s a boring statistic for you: If cold water is deprived, it will take one second of pure hot water to burn (third degree) an average person, for children and the elderly it is a closer to 0.5 seconds. A thermostatic valve will adjust or cut off the water supply in 0.3 seconds. That’s a pretty compelling safety feature.

It probably seems quite conclusive that our recommendation would be to opt for a concealed, thermostatic shower valve.

As with most shower components, you will have to buy the valve and faceplate separately.  By way of example, a universal Hansgrohe valve costs £90 and a faceplate, depending on what features you want on it, costs around £450. The more you put on it, the more it costs.

A word of warning: although you can mix and match components in your shower – for example, a Hansgrohe valve with a Vado showerhead – this is not the case with the valve/trimset combination. They MUST ALWAYS come from the same manufacturer.


  1. I recently had to have my shower valve replaced twice within just a couple of weeks. A friend of mine put it in the first time and didn’t install it properly. It was an internal valve and it leaked water into the wall space. I had to have a plumber come out and fix the problem, as well as repair part of the floor around the bathtub. I guess trying to have the problem fixed cheaply really ended up costing me a lot more. Next time, I’ll bite the bullet and have the professionals out first. It just makes more sense and will save me a lot of headaches!

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