[Closed] dripping mixer tap plumber help please

Turn it off at the stopcock, otherwise cold water will spray out everywhere when you dismantle it (the cold will be a direct feed from the stopcock and the cold that goes into the combi a spur from that).

What he said, unless the cold is fed from a tank in the loft in which case you'll need to either plug that or drain it.

As above, turn stopcock off.

Chances are the cartridge in the tap is gone, you can get generic ones from Screwfix for about a fiver but if it's specific to the tap you'll need to know manufacturer/model etc.

Slight thread hijack, what if the stopcock doesn’t turn the water off completely? There’s still a very weak stream coming out of the tap with it turned as far as you can get it (even tried putting a bar on for more leverage).

Turn it off at the meter, there should be a valve there, ours is a big plastic one under the manhole cover with the meter in the street.

Turn a tap (or taps) on downstairs, with any luck the flow out of that will be greater than the flow through the stopcock. Had to do this to replace the ballcock on the tank in the inlaws loft, the stocpcock barely had any effect so I just turned on the kitchen and downstairs loo taps (and flushed the downstairs toilet) which were upstream of the tank.

Or get a freezer pack and freeze the pipe so the stopcock can be replaced.

And finally, put some isolation valves on the hot and cold feeds while you are on the job. For next time.

unless the cold is fed from a tank in the loft in which case you’ll need to either plug that or drain it.

Good point - I had never considered that might be the case but a retrofit might be set-up like that (although I would have thought it wouldn't be recommended).

Our current house is the only out of five we've lived in where there the cold taps are not supplied via a cold tank in the attic (and having lots of water pressure here, it's great). I never understood the point of a cold tank...

I never understood the point of a cold tank…

In an indirect system, one point - usually the kitchen sink - is fed directly from the rising mains, which then supplies the cold-water storage cistern. The remaining draw off points are fed from the cold-water storage cistern. This system is designed to be used in low-pressure water areas where the mains supply pipework is not capable of supplying the full requirements of the system. This type of system also has a reserve of stored water in event of mains failure.

So your property is probably in a low pressure area, that is why you have a cold-water storage cistern in your loft. The advantages of indirect systems are that there is:
> a reserve of water should the mains supply be turned off
> reduced risk of system noise sue to lower pressure
> reduced risk of wear and tear on taps and valves, again due to lower pressure
> lower demand on the main at peak periods

That makes sense, the pressure in our old house was terrible. In this house I had to swap the hozelock fittings for their metal range because the plastic ones couldn't handle the pressure, but the shower is *excellent*.

I thought it had something to do with air gaps and preventing backflow? Anything taken off the mains supply has to have a double non-return valve, apart from the kitchen sink which has a bigger air gap.

We've got plenty of water pressure as demonstrated by the fact the 'mixer' barely works, the cold fills the sink in seconds, the hot takes ages! Should probably stick a regulator in there.

unless the cold is fed from a tank in the loft in which case you’ll need to either plug that or drain it.

Unless whoever fitted the boiler is REALLY shonky, you definitely shouldn't have a cold water tank with a combi boiler. The supply pressures to hot and cold outlets would be hugely imbalanced for starters.