Replacing kitchen mixer tap

FreeBear

Go for a pack of these - https://www.screwfix.com/p/isolating-valve-15mm-2-pack/65251

Doing the nuts up tight is going to be fun, so you'll have to get creative and bend the pipes unless you want to get the blow torch out and do a little plumbing work on the cold pipe.

grumbler

Benny2020 said:

So if i cut the pipes at the appropriate point for the flexible hoses to reach i then need something like this?
https://www.diy.com/departments/jg-speedfit-push-fit-coupler-dia-15mm/34396_BQ.prd to attach the flexible hose to the cut off pipes?

No. Compression fitting connects directly to a cut pipe. You can buy a hose with a push-fit connector, but I don't like them.

Benny2020

There is only 5mm between the hot and cold pipes so I don't think I can fit any connections to either pipe.
This is a tough one.

grumbler

I think, after cutting you'll be able to spread them easily.

Just make sure that the connectors are slightly in different positions.

Also, you can cut the horizontal part of the cold water pipe and add a compression elbow with a short piece of pipe

 

Bendy_House

Benny, I'm guessing you are fairly new to plumbing, so making soldered fittings will not be on the cards? So you'll be using either brass compression fittings, or plastic push-fit's? That's fine, and this will be a nicely challenging job to cut your teeth on!

The only complexity is the reduced access, but I think there's a way around that. But I need to get to my PC SO's I can add to your pic.

Bendy_House

The plumber who did this made a neat job of it - the swine. That makes it harder for you!

Ok, I think this is what I'd recommend. Water off - do you have a combi or storage tanks? If the former, then all you should need to do is shut off the mains stopcock, and both the H&C should stop. There will be water in the pipes, so get ready to catch this + lots of towels.

I think I'd cut the horizontal pipe and remove a section where the 'yellow' is; remove ~1.5"? and rejoin using a compression union. This will separate the two vertical pipes allowing room to work on them and fit isolating valves, and also give you more manoeuvrability in general. (Mark out where both cuts will be before cutting. Keep at least 3/4" from the soldered fittings to allow space for your nuts and olives, and keep the small copper pipe you remove - could be useful in future).

Then cut the two verticals at around 'orange'. You'll fit isolating valves on these, of the type that depends on whether you go copper tails or flexi. You can then turn the water back on to the rest of the house.

For copper tails, then normal 15mm compression isolating valves will do, as linked to by t'Bear. For flexi hoses, you will need 'flat-faced' isolating valves, as the flexis will have rubber washers to sit against these faces. Eg: https://www.amazon.co.uk/15mm-Faced-Isolation-Service-Valve/dp/B077GCVM3L - assuming your flexis have the usual 1/2" BSP ends.

You will find it MUCH easier to use flexis - in fact copper tails will be a 'mare unless you also cut the LH pipe and add a slip-coupling. If you think about it, the copper tails can only fit from one direction, and that's straight downwards. So, unless you have movement in the plumbing (you will in the RH pipe since you are fitting that horizontal union), you'd need to lower the tail AND tap together down from above and into the valve, before then bolting down the tap on the sink!

The biggest 'mare you can often have with flexis is if they are too long, so you need to have them curving away just to use up length, before then bending back to connect - they don't like tight curves.  

The above is only a suggestion. Think it through, and make sure you understand it before starting, or you might work out a better approach.

You will need the small cutter linked to before, and I'd also recommend a tin of jointing compound for potable water. You lightly smear this on to threads (and I also do the olive) and it'll help do up the fittings.

You'll also need a good adjustable spanner for the compression nuts, and a joint-plier ('water pump' plier) for holding the fitting's bodies when doing up the nuts.

Benny2020

Thanks for that, plenty to think about.
I need to make a plan.

Bendy_House

If you intend to continue with DIY plumbing - and I hope you do - then it'll be worth tackling. If, instead, you are thinking it more a one-of, then prob best to get a plumber; they'll make short work of this, probably using solder slip-couplings.