Concealed Bath/Shower mixer valve and wall cavity...

[JoelyP]

Hi all,

I'm currently getting all the plumbing in place to install a new bathroom and would be very grateful for some advice. This morning i have channelled out the hole to fit the concealed shower valve, however, the valve required a 110mm recess and the blockwork is only 130mm.

I chain drilled the outline to the correct depth but inevitably when chiselling i found myself into the cavity (the top middle part was the top corner of a block that fell off! otherwise it would have been a fairly neat cut). My question is basically... does this matter or should i do something in the cavity? the wall will be tiled and the shower valve controls mount around a steel plate as per the outline in the pic.

Also, the fittings for the pipework are very deep in the walls, would the best solution be to put a 90degree fitting coming back out and then a second 90degree fitting to run just inside the wall?

Any advice welcomed

 

[Richard C]

Afraid you can’t do that my friend, it's a definite a no no . This is one of the problems with concealed valves; you need to fill it all back in & build a false stud wall to accommodate the valve & pipework. It is acceptable to chase the wall to accommodate part of the valve & the pipework but no more than 1/3 of the depth of the internal blocks.

 

[mysteryman]

Don't bridge the cavity, whatever else you do. Are there three knobs on this control?

 

[Richard C]

Don't bridge the cavity, whatever else you do.

Don’t bridge the cavity

You can't leave it like that, it’s total bodge, breaches Building Regs & is liable to lead to all sorts of problems with cold spots & damp ingress & if he cuts much more of it away for the pipe work, it may well affect the stability of the inner block wall.

 

[JoelyP]

fill it in? can i fill it with the valve in place? is there nothing i could do with the far 20mm of the hole to prevent problems?

how/why would i bridge the cavity? yes there are three controls to the valve, temperature, flow rate and selector

 

[JoelyP]

by the way, the window is just above out of shot in that photo so its not under too much load in the area.

 

[Richard C]

fill it in? can i fill it with the valve in place?

No of course you cant; well I suppose you can do anything but it would be insane. Your going about this in completely the wrong way; if you want advice on how to do it properly, I’m quiet happy to oblige but I’m not going to get involved with what you currently doing.

is there nothing i could do with the far 20mm of the hole to prevent problems?

Remove the valve, repair the damage you’ve already done & start again after properly researching & planning your project properly.

how/why would i bridge the cavity?

Mysteryman is concerned that if you bridge the cavity damp will track across from the outside skin but you’ve already significantly breached the cavity & havn’t even got the delivery & shower head pipes in yet. Breaching the cavity will in any case give you problems with cold spots & damp; that’s ignoring the fact that you’re not supposed to run anything inside the cavity.

by the way, the window is just above out of shot in that photo so its not under too much load in the area.

That’s going to be an interesting shower, how does that work then ? Where/how are you mounting the shower head

Not sure you have the right location for your shower.

 

[JoelyP]

thankyou for taking the time to advise richard.

i do apologise but i dont understand how i have bridged the cavity? i dont want to run the pipework inside the wall cavity, i wanted to use the 90degree fittings to bring the pipework closer to the bathroom side of the blockwork so the channelling isnt too deep.

this pic shows the planned layout for the bathroom... still got the lovely 70's mint green suite in at the mo! i have a new shower bath to go in the same orientation so the shower head will be out to the left. i didnt want to put the valve on the shower head wall for two reasons: 1: the shower head wall is a 'potted' partition wall and isn't deep enough to house the valve (it is such a small bathroom that i cannot afford to lose space with falsework) and 2: ergonomicly, its a pita to reach round and move the glass shower screen to turn the shower on and you dont get a wet arm when you first turn it on!

 

[JoelyP]

when you say 'breached' the cavity you mean the fact that its an open space from the cavity to the bathroom in that area?

 

[Vehlin]

Breached in your case means you've made a ruddy great hole in your internal wall into the cavity. Take the valves out, rebuild the blocks wall inside and have another think about how you're going to deal with the issue. Are the walls at the top and bottom of the bath External too?

As pointed out before you could make a stud wall up against the window, pull the bath out by 120mm or so and mount the valve in the stud. If you don't have room for that then a surface mount is your only option.

 

[Richard C]

i do apologise but i dont understand how i have bridged the cavity?

You haven’t bridged the cavity (yet); what you’ve done is breached the cavity; i.e. made a bloody great hole in it.

i dont want to run the pipework inside the wall cavity, i wanted to use the 90degree fittings to bring the pipework closer to the bathroom side of the blockwork so the channelling isnt too deep.

Well that’s good but it’s going to be a torturous pipe route which will do nothing to help water flow/pressure; is this to be a pumped shower? What pump do you have?

this pic shows the planned layout for the bathroom... still got the lovely 70's mint green suite in at the mo!

We had one of those when we first moved here in 2004 with an almost identical bath/window & shower curtain layout! Ere you don’t live in the identical house next door do you

Just joking, I can see your still in Essex (god help you) where I lived all of my previous life

i have a new shower bath to go in the same orientation so the shower head will be out to the left.

How do you propose to run the pipe work from the mixer to the shower head? Again, looks like it might be a rather torturous route which will restrict flow.

i didnt want to put the valve on the shower head wall for two reasons:
1: the shower head wall is a 'potted' partition wall and isn't deep enough to house the valve (it is such a small bathroom that i cannot afford to lose space with falsework)

Do you have any space at all on the R/H side of the bath?

2. ergonomicly, its a pita to reach round and move the glass shower screen to turn the shower on and you dont get a wet arm when you first turn it on!

It’s the normal way to do it & you won’t get a wet arm if you’re quick enough; but, hey, you won’t have any clothes on anyway .

With over bath showers you have to be careful what type of head you fit; anything other than a rain/drencher head on an over bath shower usually results in a very wet bathroom floor unless you have two opposing bath screens.

I moved my own bath onto the wall on the r/h side (but I guess you don’t have room for that) made the window smaller & hung the shower over the end of the bath.

Just in case you havn't realised, I'm not just DIY.

 

[JoelyP]

You haven’t bridged the cavity (yet); what you’ve done is breached the cavity; i.e. made a bloody great hole in it.

gotcha and thanks vehlin for the input also the walls either end of the bath are both internal.

Well that’s good but it’s going to be a torturous pipe route which will do nothing to help water flow/pressure; is this to be a pumped shower? What pump do you have?

yes it is to be a pumped shower but i am yet to choose a pump...

We had one of those when we first moved here in 2004 with an almost identical bath/window & shower curtain layout! Ere you don’t live in the identical house next door do you

Just joking, I can see your still in Essex (god help you) where I lived all of my previous life

lol! believe me i'm not in essex by choice... have to follow the work. though this time we are pretty settled and have our first baby on the way

How do you propose to run the pipe work from the mixer to the shower head? Again, looks like it might be a rather torturous route which will restrict flow.

i have channel out that wall for 15mm piping up to the shower head...

Do you have any space at all on the R/H side of the bath?

i've got this suite to install which, as you can see, has a section that goes over the end of the bath where it could be fitted but its not an ideal location when bathing...

It’s the normal way to do it & you won’t get a wet arm if you’re quick enough; but, hey, you won’t have any clothes on anyway .

With over bath showers you have to be careful what type of head you fit; anything other than a rain/drencher head on an over bath shower usually results in a very wet bathroom floor unless you have two opposing bath screens.

I moved my own bath onto the wall on the r/h side (but I guess you don’t have room for that) made the window smaller & hung the shower over the end of the bath.

Just in case you havn't realised, I'm not just DIY.

unfortunately we don't have the room to move the bath. i was originally going to extend the bathroom into the adjacent bedroom but since the news of expecting we axed that!
the fixed shower head is just a 15mm pipe with a 90degree to the end and a 30mm round head.

 

[Richard C]

yes it is to be a pumped shower but i am yet to choose a pump

Make sure you understand how to design & install pumped systems before you rush out & buy a pump even if your getting someone in; we get many posts on the forum asking why their new pumped shower doesn’t work properly & even some plumbers get it wrong. It’s not rocket science but you must select the right pump for your system & follow some basic rules for H/C water capacities, locating the pump & deciding pipe routes/sizes.

i've got this suite to install which, as you can see, has a section that goes over the end of the bath where it could be fitted but its not an ideal location when bathing...

unfortunately we don't have the room to move the bath.

But if there is a cabinet going behind the bath as in the picture, you do have the space. Personally I would re-think the layout & fit the mixer valve, pipe work & shower head into/behind a false stud wall at the end of the bath. It’s the obvious way to go & IMO it will look & work far better than what your proposing.

the fixed shower head is just a 15mm pipe with a 90degree to the end and a 30mm round head.

I assume that’s 30cm not 30mm! Bear in mind large drencher heads require a fairly high system capacity/flow rate & with the mixer valve in the current location, it’s going to be a fair distance from the shower head & a bit of a torturous route for a 15mm pipe feed!

 

[JoelyP]

Make sure you understand how to design & install pumped systems before you rush out & buy a pump even if your getting someone in; we get many posts on the forum asking why their new pumped shower doesn’t work properly & even some plumbers get it wrong. It’s not rocket science but you must select the right pump for your system & follow some basic rules for H/C water capacities, locating the pump & deciding pipe routes/sizes.

after researching i've decided to go for a salamander RHP50 house pump. ideally i would install it under the bath so it would only come on when flow is selected from the shower/bath valve but there will be tap-offs for all the other services between the cws and hot water tanks and the pump which is a no no according to the manufacturers intructions. i dont really need everything else boosting so it will be a waste of pump lifespan and unnecessary noise if i just plumb it in the airing cupboard... so i'm considering making separate tap offs to install the pump in the airing cupboard and routing new pipework to the bathroom. i'm just finalising what components i need inline between the pump and the valve as i want to take the pipework through the loft (not a viable option to rip up floor boards).

 

[SteNova]

we had a simalar issue in my parents shower room, in the end we put 3" battons on the wall then covered it over with multipanel, all the pipework is hidden in the void beween the brick and multipanel,

edit, just read you can't loose any to a false, maybe you can mount a surface one on the window sill