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Servicing the CD valve in a leaky tap

Ceramic Disc Valves are widely used in new taps. I have written a post detailing the reasons for this here. If you find that your CD valve is dripping or that it is grainy in its operation, you may need to service it. This can be necessary when grit and debris gets into the valve. This can be prevented by using filters/strainers in the plumbing installation but sometimes these valves need to be serviced or replaced. Hopefully this post can help you if you have an issue with one of these valves. The valve detailed below is a Quarter Turn Brass Housing Valve usually used in taps with separate Hot and Cold handles. There are plastic versions of Ceramic Disc Valves for one handle Mixer type taps (these have one handle for both flow and temperature control).

Tools required: Adjustable Spanner/Socket Set, Allen key set, Stanley Knife, Flat Head Screw Driver, Warm Soapy Water, Clean Cloth and WRAS approved Grease.

If you are not confident it is best to get a trained professional plumber to do this but this is a relatively simple task that can be completed in about 30 mins all going smoothly.

Lets start with the above exploded view CAD model I created using the Inventor 3D CAD Software some time ago. This details the various components and also the typical materials used in one of these valves. Valves differ but this will be the general makeup. Below is a real life exploded view of a simpler design with less components. I have given them the same titles as in the drawing for clarity.

To service this valve you first need to remove it from the tap. To do this:

1. Turn off the water at the nearest isolating valve and at the mains. Then open the tap and drain the remaining water away. This is important to prevent a flood, especially if there is mains electricity nearby.

2. Remove the handle from the tap. First you will probably need to remove the button that marks Hot and Cold using a blade like a Stanley knife. Underneath this there is usually an Allen Screw holding the tap handle in place. Turn this anticlockwise to loosen and remove the handle by pulling away from the tap. I have written a post here with images on how to do this here.

3. The Ceramic Disc valve should now be exposed. Remove the Ceramic Disc Valve using a spanner or a socket (preferably to stop rounding of the flats) by turning anticlockwise. Use WD-40 if it is tight.

4. At this point the ceramic disc is free from the tap housing. We can now start to dismantle the ceramic disc and service it.

5. Remove the Circlip (see exploded view image above). This can be done by pushing it with the flat of a screw driver or a Circlip tool. This releases the spindle.

6. Push the spindle towards the face seal (blue seal in Image above). This will release the spindle, the Ceramic Disc Valves and also push out the Blue Seal. At this point, clean the various O-Rings and the Ceramic Disc Valves with warm soapy water to remove debris and limescale. When finished, grease the Ceramic Discs and the O- Rings with a WRAS approved grease before reassembling. It is worth taking the time now to clean the tap with warm soapy water to ensure there is no debris where the valve sits in the tap or around the O-Ring that seals the tap (on the brass housing). If there is obvious damage to the Ceramic Discs or damage to the Seals/O-Rings, then you will need a replacement. Contact us here for replacements.

7. The Spindle end fits into notches on the parts marked Ceramic Disc 1 in the above exploded view. The Ceramic Disc 1 presses up against Ceramic Disc Valve 2. Take this assembly (Spindle and both Ceramic Discs) and put it back into the Brass Housing. There are guide features on the Ceramic Disc 2 that run inside notches on the Brass Housing to make sure that it goes in correctly.

8. Now you can put back on the Circlip using your fingers or a circlip tool.

9. Replace the Face Seal in the bottom of the housing.

10. Put the assembled Ceramic Disc Valve back in the housing by hand tightening (clockwise) and then nipping up with a spanner. Please be careful not to over tighten this.

11. Replace the handle. Make sure the spindle is turned to off before doing this or else the handle will be in the incorrect position when tightened. Tighten the Allen Screw and replace the Hot and Cold Button.

12. The last step is to turn back on the mains and open the isolating valves slowly to check for leaks. When you are sure there are no leaks, open the isolating valves fully.

That is it! Hopefully this has cured your leaky valve. If it did not, then you may need a replacement. We can help with this as we supply replacements for all your models. Simply tell us what tap you have bought from us and we will send you a quote for a replacement. Please see here for contact details.


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