What is a thermostatic shower – How does it work

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There are basically two ways to get your shower water to just the right temperature.  You can mix hot and cold water or you can heat cold water.  Most showers mix the hot and cold water feeds.  Thermostatic showers do it much more efficiently than manual ones.

What is a thermostatic shower

What is a thermostatic shower?

A thermostatic shower is a shower which automatically maintains your chosen water temperature without any action on your part (other than setting it).

Thermostatic showers work with the three main types of water system in the UK.  They are most popular in households with mains-fed hot water systems and combi-boiler systems because both of these are notorious for the ease with which water flow can be disrupted by other people’s actions.  This can even mean the actions of people in different properties.

Gravity-fed water systems tend to be more dependable, but even with them, thermostatic shower valves are often seen as being a useful extra safety feature “just in case”.

how does thermostatic shower work
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How does a thermostatic shower work?

A thermostatic shower works by using a thermostatic valve to mix the hot and cold feeds in the correct ratio before sending the water through the showerhead.  Because there is a link between water temperature and water pressure, this also maintains a steady flow.  Modern thermostatic showers will also shut down automatically if they detect that the cold-water supply has dropped below a safe level.  This prevents scalding.

Thermostatic showers are not electric.  They simply store hot water from the mains and then mix it with the appropriate quantity of hold water to create the right temperature.  Electric showers take cold water from the mains and heat it up to the desired temperature.  To put it another way, thermostatic showers work in much the same way as mixer taps whereas electric showers work in much the same way as kettles.

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How does a thermostatic shower valve work?

There are four key parts to a thermostatic shower valve.  These are the temperature control, the thermostatic element, the piston and the return spring.  Some also have a diverter so you can choose between different outlets such as the main showerhead and a hand-held showerhead.  In fact, some even have more than one diverter.

The temperature control does exactly what its name suggests.  It allows the user to set their desired temperature.  As the water starts to flow the thermostatic element measures its temperature and reacts accordingly.  If the water gets hotter, the thermostatic element expands and if it gets hotter, the thermostatic valve expands.

The thermostatic element controls a piston and a return spring.  These move across the hot and cold water portals maintaining the correct temperature.  For completeness, if the temperature rises above a safe level (e.g. the cold water supply fails), the element will expand to a point where at least the hot portal would be covered.  These days usually both portals would be covered.

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Buying a thermostatic shower valve

Once you have worked out what functionality you need, you then have to decide whether you want an exposed thermostatic shower valve or a concealed thermostatic shower valve.  Exposed thermostatic shower valves may not look very visually appealing (although this is arguably a matter of opinion) but they are easier to maintain.  Concealed thermostatic shower valves can look very sleek and very much in keeping with a minimalist aesthetic, but they can be inconvenient to maintain.

Whichever type of valve you choose, it’s advisable to look for one which has a high build quality.  You want components made out of strong material, chrome-plated brass is very popular for higher-end thermostatic shower valves.  Ideally, you want the components to be removable, again this is for ease of maintenance.

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Thermostatic shower valves for over-bath showers

You can buy thermostatic shower valves for over-bath showers, you will just want a diverter to switch between the shower and the bath taps.  For completeness, you can also get thermostatic taps.  These are similar to regular mixer taps except thermostatic taps will adjust the water inputs to maintain your desired temperature.

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Thermostatic shower valves for caravans and camper vans

You can certainly get thermostatic shower vans for caravans and camper vans.  In fact, you can even get thermostatic shower valves for over-bath showers in caravans and camper vans.  Thermostatic shower valves for caravans and camper vans are slightly different to regular thermostatic shower valves so you may have to get one from a specialist caravan/camper van store rather than a bathroom store.

Keep it clean and maintain
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Maintaining a thermostatic shower valve

The easiest way to avoid problems with your thermostatic shower valve is to keep it clean.  This is particularly true if you live in a hard-water area.  Ideally, you’ll fit a water softener, but if this is not possible, then you need to be thorough about treating limescale. 

To do this, remove the thermostatic shower cartridge and soak it in a solution of at least 50% vinegar plus water.  You might even want to use neat vinegar if you can live with the smell.  Alternatively, you can buy shower descaling products.  They won’t necessarily be any stronger but they may smell better.

Leave the thermostatic shower cartridge to soak for at least an hour and then replace it.  This might also be a good time to soak your shower head too (for the same reason).

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Repairing your thermostatic shower valve

In principle, many thermostatic shower valves can be repaired or replaced.  As the quality of the thermostatic shower valve increases, so does the likelihood that you’ll be able to undertake at least some repairs (or have someone else do it for you).  In practice, depending on what the problem is, you may find it simpler, more affordable and more effective just to get a new shower. 

That said, if you have problems with your shower keeping the right temperature, you might want to look at other possible issues, before concluding that there’s a problem with your thermostatic shower valve.  In particular, check for blockages in the showerhead, shower hose and inlet filters.  These are possible even in soft-water areas.  If you live in a hard-water area, then you’re back to the known issues with limescale.

Katie Mills

Katie is the Editor here at Poshh Living and is a well-respected voice in the world of design and home improvement. Katie has a first-class Hons degree in Journalism and is proud to say that she has written many leading entries in the biggest media outlets including Ideal Home, and Good House Keeping. Lover of the great outdoors and mother of two, Katie is 'down to earth', knowledgable and a great asset to the team

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