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The Shower Doctor Surgery: How to service a Mira 88 shower valve

Posted in DIY Tips and Guides on by
The Shower Doctor Surgery: How to service a Mira 88 shower valve

Your Mira shower valve will undoubtedly need a little TLC from time to time as the internal seals can become worn, so a service will do it wonders. In fact, a service will most definitely be required if your water flow seems reduced or you have a leakage problem.

This guide will show you how to fit a service pack to a Mira 88 shower valve. It can also apply to the Mira 8 valve, as both are largely the same except for a couple of minor differences.

You will need:

 

Disassembling the valve

Remove the temperature knob by fitting a screwdriver into the slot underneath and levering it off. Then, you'll need to lever off the horseshoe clip that holds on the main knob. The cover of the valve should just pull forward and off, and underneath you'll see a metal plate that holds the unit in position. Unscrew the screws and take off the plate

Removing the temperature knob.
Using a screwdriver to pull the temperature knob off the valve.

 

Next remove the main knob, which should just pull forward. If it is tight, you can use boiling water to help expand the plastic or a couple of screwdrivers to help lever it forward. Now you can take off the large brass nut with a wrench. Again boiling water will help to expand the brass if it is too tight, or you can use a hammer and give it a few sharp taps all the way around.

Using hammer to loosen the brass nut.
Boiling water or a few sharp taps with a hammer help loosen the brass nut.

 

If you are using this guide for a Mira 8 you'll notice that this valve has a very small nut that can be difficult to get to, so you will need to use a smaller wrench.

Once the nut is removed you will see the main workings of the shower valve underneath. They consist of the part that controls the water temperature and a halter with hot and cold pistons. Pull these out, disassemble them and lay all of your parts out so you can see and identify them.

Reassembling the valve

Now it is time to reassemble your valve and replace your old washers and seals with new ones from the service pack. In the pack you'll find a piece of paper which shows all of the different seals. They are all letter coded, and there is a diagram showing how they all fit onto the various valve parts. Some are very similar in size, so the best thing to do is to match them up with the images on the paper so you can be sure you're fitting the right bits.

Matching seals with Mira diagram included in the service kit.
Matching seals with appropriate drawings on paper Mira diagram is the best way to make sure no mistakes are made.

 

Start with the hot and cold pistons and use a tool with a point to remove the old seals and place the new ones on. Next, reassemble the halter and the water temperature controls according to the instructions in the service pack, making sure to put any washers, springs and other parts back on in the correct order.

You should grease the new components as you go as this will make it much easier to take the components apart the next time. Mira does supply some grease in the pack, but we much prefer our own branded Showerdoc silicon grease. Once the inner workings are reassembled, go back to the shower and place a new washer into the hole in the middle, making sure that the old one is removed first. Then push the temperature control components back into place, checking that the pistons can move freely back and forth when you press them in. Putting temperature controls back inside the valve.

Once the temperature controls are back inside the valve, make sure they can move freely back and forth.

 

A large plastic washer fits around the outside and a copper thrust washer needs to be placed onto the front before the cover plate can be screwed back on. Replace the seal on the cover plate by pushing it into place and screw the whole thing back on.

The inside mechanism has a tendency to turn at the same time, so you'll need to turn this back anti-clockwise to allow you to screw the cover plate on tight enough. Push the handle back on and replace the horseshoe clip, which holds the handle in place. Finally, replace the temperature control knob.

You may find it much easier to refer to our Mira 8, 88 & 88B video service guide when reassembling the valve so that you can see the various parts for yourself and the order in which they are put back together.

Full video:

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About Us
George Thomson established "The Shower Doctor" in 1993 to focus on shower repair in the Edinburgh area. George is a second generation plumber; he and his father ran a successful plumbing and heating business. In the late 80's this 40-year-old family business was sold.
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