Has Your Thermostatic Cartridge Failed? – Read our Guide

One of the most common parts to fail on a steam or shower cabin, particularly on older models is the thermostatic cartridge.

Symptoms Include:

  • Unable to regulate the water temperature
  • Only cold or warm water
  • Only scorching hot water
  • Stiffness in dial when adjusting

If you are unable to regulate the temperature and you are getting only cold/warm water or conversely very hot water from your shower, it is an indication that the thermostatic cartridge has either failed, or is failing. Another symptom can be recognised by stiffness in the knob when you try to adjust the temperature.

Why Has It failed?

There are several reasons why the cartridge may have failed; the number one cause is an imbalance in water pressure between the mains cold pressure and the heated hot water. This constant in-balance between the two will cause damage to the cartridge which is housed within the valve. Fitting a PEV (Pressure Equalising Valve) can resolve this. Note it will not fix an already failed cartridge.

Another reason could be down to muck in the system, perhaps the plumber used flux to solder pipework and this wasn’t flushed through, again due to the delicate nature of thermostatic cartridges, the debris can damage the part.

Hard limescale build up is another cause for the cartridge to fail. So if you live in a hard water area, it certainly pays to install a softener, these are not always expensive as people think, and a simple inline device like the Scale Wizard will drastically reduce the build-up of calcium deposits. Not only that it will assist in keeping you cabin glass cleaner as well as furring up of the hand shower, hydro jets and monsoon and most importantly the Steam Generator if you have a model fitted with this feature.

Replacing a Thermostatic Cartridge

To replace the failed cartridge is not a difficult task, all the work is done from inside the cabin, so moving the whole unit out is not necessary. We have put together an easy to follow how to guide here.

What Cartridge type do I need?

Unfortunately, even if you know what brand and model of steam or shower cabin you have it will not help us to advise which type you need, over the years models are fitted with varying types of valves. These valves generally house one of two different types, although there are a couple other types that we will explain further down.

Type 8 – This is a screw fit type – The most popular by far, easy to identify by the screw thread to the top part of the cartridge, you will also be aware that you had to screw it out of the valve housing when removing.

You have the option of purchasing the Type 8 Vernet cartridge; this is a branded cartridge and is fitted with a wax sensor, proven to be far more reliable and efficient than the regular type. Brands such as Insignia and Aqualusso now fit these as standard to most new steam and shower models these days.

 Type 6 – This is a push fit type – The second most popular type, again easy to identify as this pushes into the shower valve housing, you would also be aware that you had to remove a small grub screw from the underside of the housing when removing.

Same as the Type 8 above you have the option of purchasing the branded Vernet Type 6.

Other types include the Colorspa Cartridge. If you have a Colorspa steam or shower cabin then this is the only cartridge that will fit your shower valve.

Type 12, fairly uncommon, these are very similar to the type 6 in that, in that it is secured into the housing by way of a grub screw, but you will notice the gauze section is much wider.

With models such as the Type 6 and Type 8 where you need to also replace the plastic temperature safety lock please visit the thermostatic cartridge page of our store


[box type=”download”]Don’t forget to download the easy to follow document showing you how to remove the tool below.[/box]

steamshowerparts.co.uk is, of course, UK based, however, we ship all parts listed in our store worldwide ( except for Long items such as door seals etc) If you are US based and looking for a steam bath installer just click the link for more information.