The Shower Doctor Surgery: How to service Gummers 1800

This guide will explain how to fit a service kit to a Gummers 1800 series valve. This particular valve is used by a number of different shower manufacturers, who have each put their own knob sets on it.

So although yours may look a little different to the one in the instructional video that accompanies this guide, once you get everything stripped down the cartridge inside will be exactly the same.

You can buy your service kit and any other spares you may need from The Shower Doctor.

You will need:

  • A tool with a point
  • A pair of circlip pliers
  • A knife or small screwdriver
  • A large wrench or similar tool

Stripping down the valve

Begin by stripping off the knobs on your valve. With the Bristan valve - which is the one shown in our instructional video - you start by taking off the nameplate using a knife or a very small screwdriver.

You'll find a small screw underneath and you can use a Philips screwdriver to remove this. You may need a flat-headed screwdriver to get into the valve depending on the type of shower you have.

Once the screw is removed the temperature control knob, the dial, the on-off knob and the surround should then pull off.

If they are tight, you can pour a kettle of boiling water over the knobs to expand the plastic. You may also find that in some models the main knobs are held on with a circlip, which can be removed with a pair of circlip pliers.

Next you need to remove the cartridge assembly itself. It should screw off using a large wrench or similar tool.

Inside you'll find the piston - or the shuttle as it's also called - a spring and a wax capsule that controls the thermostat function. Remove them carefully and set everything aside.

Replacing the seals

Next you need to replace all the washers and seals in the cartridge assembly using the new ones in your service pack.

You can of course just buy a new cartridge assembly and simply screw it back in, but it does work out a lot more expensive that buying the seals alone.

Take the cartridge to pieces and remove the small circlips at the front using your pliers. Then give the cartridge a tap with the end of a screwdriver until the components come through.

Now take the rest of the cartridge to pieces. Pull out the bit that adjusts the temperature and you'll be left with the main part of the cartridge.

Empty out your seal kit onto a table so you can see them all clearly. Because there are various versions of the Gummers 1800 valve there will be some seals inside the kit that you won't need.

Take the seals off the main part of the cartridge using a pointed tool and one by one replace them with a matching seal from the kit.

One of the seals in particular can be very tricky to put back on, so you can use a cup of hot water to help. Simply pop the new seal into the water and leave it for a few minutes to warm up.

Greasing the seal will also help. Grease is supplied in the service kit, or you can buy Shower Doctor's own brand silicone grease here.

Replace the smaller seals on the other parts of the cartridge, and then the two inside the body of the shower valve. You'll find one at the front and one towards the back.

Reassembling the valve

Grease all the new seals and then put the circlips back on using your circlip pliers. Now you can fit the cartridge back into the shower.

Put the cartridge and the wax capsule back together, followed by the piston and the spring.

When putting the spring back into place, use a screwdriver to lever out the edge a tiny bit so that it will fit more snugly into the piston.

This ensures it won't fall out when you try to put the cartridge assembly back into place. Screw it in using your wrench to tighten it up. Then all you need to do is refit the knobs.

You may need to reset the temperature on your shower once you switch the water back on. You'll find a short video showing you how to do this here.

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