Introduction: Servicing an Aqualisa Aquavalve 605/405 Thermostatic Shower Valve (Old Style)

About: I like to look at things from a different position. Just because someone tells you its not possible they usually mean un- profitable

There are other article on the new type plastic style Aqualisa Mixer, that the information on how to remove the cartridge is covered elsewhere on Youtube. Nowhere could I find information on servicing this older brass type of valve, or how to dismantle it so that I could replace 'O' rings inside. I can confirm what qhurtle wrote :Servicing a Plastic Cartridge , that most if not all of of these valves are very similar in construction. Although some are harder than others to take apart.

This project on indestructible , simply shows you how to open the controller so that the 'o' rings can be replaced from a supplier on eBay. In 2020 the cost of a new cartridge is £107.00. The 'O' rings should cost a few pounds each. Although, mine was not in good condition and had a lot of lime scale deposit in it . This was removed with normal house cleaning products that you would use in your kettle.

This particular cartridge had been in place without fault since 1996. I was surprised that to remove the brass cover. Very little turning force was needed. One important note about gripping the cover It has sloping edges leading towards the center to the bearing. You must grip this bearing or you will ruin the cartridge for good. I found that by winding the thermostatic valve in one direction this created some distance between the plastic body and the brass ring.


A Philips screw Driver; W5 Limescale remover tablets ; a friend who has a lathe chuck; Wooden Hammer

Step 1: Unscrew the Brass Hidden Nut.

BEWARE : Look at the item you are going to remove thoroughly. You must not grip the bearing as you will break the bearing. As discussed in part one I was able to wind the thermostat back to create a gap between the plastic bezel and the brass cover. I tightened the chuck slowly rotating to each pinion in turn tightening slowly until no more could be achieved . You need two setts of hands to undo this part .I placed the chuck on a tea towel on the kitchen table and undid anti clockwise to my surprise this came undone very easily.

Step 2: Pulling Out the Central Rod

This came out in two parts. Initially the top unscrewed which , meant some head shaking as it didn't seem to attach to anything and was only found by replacing this that the rod below it was free and could be knocked out of the bottom of the tube with a hammer and screwdriver. As you can see the cover controlling the temperature was removed by undoing two Philips screws. This enabled it to be removed for cleaning.

Step 3: Replacing 'O' Rings

Without much fuss the 'O' Rings can be removed with a needle or a dental tool which is useful for replacing the Hot water 'O' Ring. The items can be refitted in reverse I used petroleum jelly on the 'O' as it said in my documentation to do this.

I measured the slots for the 'O'rings starting at end of bar inside housing outwards . These are approximately as follows:

ID:6mm x CS:4mm x OD:11; ID:10mm x CS :2mm x OD:14; ID:8mm x CS:3mm x OD13mm.; ID:11mm x CS:3.5mm x OD18mm

From this we can work out 'O' ring sizes for which the bore of the tube that it fits into is not parallel.

I found a 18x3.5mm in a Poweflix kit of 'O' Rings.

I could not find 'O' rings for the other fitting and tried flat washers as it was all I had of the correct size. I used Vaseline on the 'O' rings to ease them into the tube

Hope this helps,

Step 4: All Went Well, Yes Its Copper Not Plastic or Brass.

I used even used some dental picks and a watch makers screw driver to remove the hot water 'O' ring at the back of the cartridge housing. This was straightforward with the correct tools I found could trap the 'O' ring with the dental tool and stab it with my sharp watchmakers screwdriver. This came out the on the end of the screwdriver with little problem. Replacing this was a little more difficult as I have large fingers . I blocked the lower pipe for the water outlet with some rag as I did not want to loose the 'O' Ring down the pipe. I used a screw driver to slide the 'O' ring back into the housing and my fingers to push it back into the channel. It seated well . I rubbed some petroleum jelly on it and put the cartridge back together.

Now a few words of wisdom the two parts of the rod are joined by a left hand screw this is coarse and is hard to get started. Don't remove the cover from the chuck until you are ready to put it back together work the thread back on gently. It should also be noted the two brass screws in the plastic bezel which the heat lever is attached too , will need adjustment, over tightening this will make the lever hard to turn . It should be noted that these do not limit the rotation but simply adjust how tight or loose this mechanism is.

Be warned if you break anything it cannot be replaced easily unless you have friends with equipment to do so .