Removing Tap Cartridge

[MTbowels]

My kitchen sink is fitted with a mixer tap and has developed a persistent drip. The tap is not the monobloc type (sorry, I don't know the opposite of monobloc!) but has a two separate feeds from the cold and hot water pipes into its base. Unfortunately, there are no service valves in any of the pipework to isolate the taps.

The tap uses ceramic tap cartridges and I've bought a replacement pair to fit using an old cartridge as a size guide. I've now discovered that the brass screw fitted inside the cold tap handle has a damaged head and I can't turn it with either a slotted or pozidrive screwdriver. It's recessed too deeply to grab firmly with a long-nosed pliers - I've tried it.

It seems to me that my only option is to drlll vertically through the screw head and remove the bits piece by piece. The problem is that I'm reluctant to do this if there's an easier way to do it. I don't think that oil or something similar would loosen the head sufficiently but I'm not certain.

Could I have some advice please on how to get the screw loose? Is drilling it out the usual way of removing the screw?

The hot water supply comes from a combi boiler to the tap and bearing in mind that there are no service valves in the pipework, what do I need to do at the boiler end to shut off the water if the hot water tap cartridge needs renewing? It's a Baxi Duo Tec 28 boiler.

Thank you.

[MTbowels]

I should have added that the replacement cartridges are fitted with new screws so I don't need to be that fussy about getting the old screws out!

[dannyk13]

You should find what you need here:-
https://www.google.co.uk/search?ei=1y5jWpXzJsvegAbJgrOwCQ&q=kit+for+removing+rusted+screws&;oq=kit+for+removing+rusted+screws&gs_l=psy-ab.12...40555.42901.0

[The Builder]

This is often a problem, MT. Danny's set may well help. It's a matter of luck really. Even a standard 3mm drill bit may do it. The idea is to remove the whole screw of course, but you may have to start by just removing the head of the screw.

By drilling off the head, you may be able to pull the handwheel off. Then, it's a matter of removing the threaded bit with the handwheel out of the way.

With a combi boiler, simply turn off the water for the whole house (usually somewhere such as underneath the kitchen sink.)

[MTbowels]

Thank you both for your very useful advice. It was exactly what I needed.

The Builder, could I just clarify the issue of the combi boiler. The rising main stopcock is in the downstairs toilet near the front doorand is simple to turn off - there are no stopcocks beneath the sink. If I turn the rising main off and dismantle and remove the hot water cartridge in the mixer tap, won't the water in the combi boiler pour out of the hole where the cartridge was sitting? I don't want to get soaked! Or do I need to turn something off beneath the boiler to stop this happening? I just thought there was more to it than simply turning off the rising main if I needed to replace both ceramic cartridges as a pair.

Thank you.

[The Builder]

You're Ok, Mt. Combis are supplied with water at mains pressure directly from the rising main. Turning that off is enough.

To confirm that you have located the rising main, turn it off and run the hot and cold taps separately to be sure ... before dismantling the tap.

I have to admit that I did once cause a minor flood after turning off what I assumed to be the supply, only to find that there was another one elsewhere. The one I turned off was something else entirely. We've all done it!

[MTbowels]

The Builder, you're brilliant. You were absolutely right about the hot water. I turned off the rising main in the downstairs toilet and turned on the hot and cold taps in the toilet. Only a pint or so of water came out of the hot water tap before both taps dried up.

The job itself was straightforward after that and was completed succesfully. Thank you again for your invaluable advice. I'm very grateful.