Mixture valve installation advice please

[kjacko]

Hi all,
So completely refitting my brothers bathroom.
Got a 800 x 1000 shower enclosure.
Concealed 2-way mixture valve which I’ve fitted.
As you can see the inlets are 22mm. I suppose I need to just use reducers to 15mm?
For arguments sake the top left outlet will go up and above the new suspended ceiling and down the other side of the enclosure to the 300mm square shower head. The outlet on the right will go down, under the floor and up the other side of the new stud wall (part of the enclosure) to feed the diverted handheld.
I’m using pex pipe pretty much everywhere, I will use copper to come out of the valve and when going into the shower head and handheld. I’m trying to use single runs of pex pipe with as few joins as possible.

Now, I know a lot of plumbers/fitters don’t like concealed valves, or pex pipe for that matter, but that’s what I’m using so no need to comment on that.

question: do I need to put check valve on both inlet feeds? If so, where. A brand new baxi combi has been installed. Pressure is good.

all advice welcome (except comments on using concealed valves)

 

[kjacko]

Just to add to my OP.
The idea is that brother can slide open the shower door and turn the shower on from the controls of the left without getting cold water splashing onto him as the shower heads are on the right of the 1000mm shower. He has cancer so he’d as much comfort (and little distress) as possible.
I’m aware that switching the diverter will produce a small delay in getting the right temperature water to that outlet due to the extra distance it has to travel from the valve.
Can anyone see this being an issue?

 

[muggles]

You could use 22×15 reducers, yes, but a better solution would be to use ¾" MI × 15mm compression fittings straight into the shower valve - reduces the number of joints used. You don't need PTFE on the thread the nut screws on to - it does nothing to seal the joint, just makes it harder to do up. I suggest you might need more on the end that screws into the valve though.

Both check valves and isolation valves would be a good idea, but they need to be in an accessible location for maintenance - above the suspended ceiling could be a good place

 

[kjacko]

Thanks Muggles. I actually thought I’d bought 22mm-15mm reducers in the bundle I purchased. I’ll check my order. But yes, those would be better.
I used loctite55 on the threads. I get fed up of hearing the arguments about when and when not to use tape, so I just do it as a default. Can’t hurt I guess. ‍
Regarding the NRV, are they full bore? And to go on hot water only or cold as well? Also I have quite a few 15mm isolators that have single directional arrows on them. Would these not act as a NRV. If not, what’s the point of having them on? Should I put one on the mixer basin that will be anew install too?
My issue will be that once finished there really isn’t any way to get under the floor or above the ceiling without damaging something.
Thanks again

 

[muggles]

Check valves are full bore if you buy full bore check valves. They should ideally be fitted to both hot and cold supplies for best practise. The arrows on the isolation valves are to show you which way round to fit them, that's all. They don't have any backflow prevention function. Fit them the wrong way round and over time the water pressure will damage them.

 

[oldbuffer]

There may already be check valves under the slotted hexagonal nuts or they may be only filters. Check the installation instructions. In either case, I'd suggest removing the nuts while you still have access, and replacing them with a little silicone grease on the threads. Make sure they are left accessible when finishing.

 

[kjacko]

Hi all, I’m back.
Well I’ve had some fun with this lot, but I think I’m on track. I replaced the inlet 22mm fittings with 22-15mm reducers. However the cold inlet weeps very slightly. I nipped it up, still weeped. I took it off, replaced the ptfe I’d previously applied with locktite55 and put it back on. And it still weeps.
WTF? I can’t see any damage on the thread.
I do have some of the ptfe paste, should I try that?
I put full bore isolators on the shower feeds with a check valve on the hot feed only, although been told as we have a new combi it’s not necessary but won’t hurt. These are now accessible by just pulling up the carpet and removing an access panel I’ve made in the floorboards.
Basin has its own 3/4 isolators on each tap, so basically the bathroom can now be isolated.
Any comments on the above please? Especially that 22mm inlet fitting that stil blood leaks.

 

[Madrab]

As @muggles mentioned, thread tape/seal/thread on the fitting threads does nothing, a compression fitting doesn't create the seal at the threads, in fact using a thread sealant can actually stop the fitting from tightening properly if there's too much used, so it needs to be removed.

The watertight seal is created at the olive when it is compressed against the pipe and the fluted faces on the nut and the fitting, so if tape needs to go anywhere then it's a few wraps around the olive.

 

[kjacko]

There is no olive. If you look at the pics of the valve (previous post) the 22mm compression just screws into the valve.
I’ve tried tightening it with nothing and it leaked, so I tried ptfe and it leaked.
When I got to site this morning I re-wrapped the 22mm thread with locktite55 and it finally worked.
Then the bloody hot feed valve started to leak, so I undid that removed the ptfe and replace with locktite55 and that’s now fixed.
THEN....the frikkin cold started to weep every so slightly again,and it’s fully nipped up.
WTF!?

 

[Madrab]

If you look at the pic again, the other end is a compression end with PTFE tape on the threads and they have olives, hence the reply.

Only reason why it will leak is, there isn't enough tape, there isn't enough thread seal, it's been tightened too much and the threads have mashed all the sealing agent up.

I use gas PTFE tape, 6/7 wraps (normal tape uses anything up to 14 odd turns) and tighten it as much as it needs - you get a feel for it - no call backs yet.

 

[kjacko]

I’ve checked the threads they ‘look’ fine. They are fully tightened.
Locktite55 does seem better than ptfe, but I put quite a bit of that onto not sure why the cold has decided to start leaking very slightly after a day of being ok. ‍

 

[Madrab]

They are fully tightened

No guarantee that'll do it, they need to be tightened 'just enough', too much and it can then burst the seal that's been made with the tape/thread. District static water pressure tends to rise overnight when usage drops and that may have been enough to push past the seal, once it's leaking it won't re-seal and needs remade.