MortarThePoint

I thought I'd start a thread of considerations to do with the plumbing. Below are some pictures that show the proposed layout. I'm presuming that I'll use 15mm for all pipes except those shown as 10mm and probably the stopcock to Water Cyclinder will be 22mm (inc manifold) --------------- -------------------

Here's an important one from the Hep2O FAQ: Q.) Can we use expanding foam on Hep2O? A.) No, due to the chemicals when in its liquid form, these could harm the pipe. Once the expanding foam has cured Hep2O pipe can be safely fed through it. Alternatively the Hep2O could be sleeved to give the required protection. https://plumbpal.co.uk/image/catalog/Documents/Hep2O_FAQs.pdf

My volume figures were wrong (school boy Maths error): Q.) How much water does Hep2O pipe hold per metre? A.) 10mm pipe = 32ml 15mm pipe = 110ml 16mm pipe = 120ml 22mm pipe = 260ml 28mm pipe= 400ml

@Nickfromwales or @Conor : sorry for the basic question, but do you do a 15mm feed all the way back to the mains supply or do you do 22mm to the room and then 15mm / 10mm to the various places in the room?

I think I understand. I was thinking it is to reduce dead volume before hot comes through, but is it to create a more restrictive path than that to the bath so the bath doesn't suffer a loss of pressure?

Good point, skinny pipes to basins for faster hot water (0.35l/m vs 1.00l/m, but more constricted). I presume HRC is a looped system that makes for instant hot water which isn't what we'll have. As this basin is about 6m from the cylinder I'll probably have a dedicated pipe for it as then it can be 10mm all the way, unless you'd be happy with 10mm for a bath feed?

The stated diameter is the OD of the pipe, so if you come across the image below ignore it. I double checked with Wavin technical. Some IDs are: OD ID Area or volume/metre 10mm 6.7mm 0.35cm2 or l/m 15mm 11.3mm 1.00cm2 of l/m 22mm 17.7mm 2.46cm2 or l/m

Here's some information about Hep2O pipe pressure and temperature. This old document has some pipe dimensions in: https://www.hep2o.com.au/downloads/Hep2o_Parts_Users_Guide_Australia_2018.pdf Here's the installation guide: F-47058-0.pdf Here's link to a performance sheet: http://www.tglynes.co.uk/downloads/tgl-coshh-tech-hep20-performance.pdf

Sounds good. When I did the UFH pressure test we had 5.5bar so will hopefully be good for water pressure. I guess we'll use 15mm allround then for water feed (not UFH), thanks for sharing the insight. Looks like you had some good service gaps in your concrete floors, but I can see some pipes coming through the concrete into the floor channel of the wall. What size holes did you use in the concrete? Did you bother sleeving the pipes as they passed through, or just filled with foam? Similarly, what did you do when passing through blockwork walls?

I'm intrigued by your mixture of water pipe sizes. You appear to have thinner and thicker water pipes. I am currently planning my plumbing so it would be good to understand.

It's our main bedroom en-suite so high likelihood of basin and/or toilet being used at same time as shower. (and yes that second bit horrifies me too).

I didn't like the sound of the extra 16seconds of wasted hot water so have punched a hole in the sole plate of the wall and the hollowcore concrete, below the word SHOWER, and the hot water feed can come up through there. I now wonder if the cold should come up there too as will turning the basin tap on affect the shower temperature?

I'm trying to plan the plumbing of the en-suite. Thanks to @Nickfromwales I know what to do with my basin waste and I show that it brown and black below (brown in the room, black is in the wall). I then need to route the hot and cold water feed (shown combined as red below) around the room to the various places. It's going to come in to the room in the corner where there is a trench in the screed along the top wall to the bath. It's going to then have to come above screed to reach the right stud wall before feeding the basins and continuing on to feed the shower. The shower and bath wastes have holes in the floor underneath the shower and bath. The feed may pop up under the bath rather than the corner, but that doesn't change much. Where a right angle is shown in pipe below there may need to be an elbow or tee. Is it a good idea to clip the fed pipes to the OSB or does that make it noisy? I am expecting to use something like push fit JG SpeedFit for the water feed, but am solvent welding the wastes. The length of pipe round the room is about 12m so if it's 15mm OD / 11.5mm ID (JG Speedfit pipe datasheet) the pipe volume is about 1.2litres. A shower running and 6l/m total and 3l/m each of hot and cold would take 24 seconds to pass that volume through. It's a bit of a shame because if I could get there direct it would only take about 4m of pipe and so take 8 seconds for the shower to heat up. Is 15mm the correct size to use to feed a shower? Bathroom wall layouts as viewed from outside the room:

We aren't considering any particularly fancy tiles so weight probably not a concern. Do you think it reduces the bond strength of the tiles to plaster though? I'm just thinking it is easier to ask he plasterer to do a whole room that mark out where he shouldn't plaster.

I can understand the concern if the crack isn't supported by material behind, but ultimately if you just treat it like a join surely(?) it can't cause any problems

I have two sheets of plasterboard that snapped whilst being carried. They didn't get dropped, but the snap is straight across and the sheet folded to near right angle. I saw in the BG book it says not to use damaged sheets, but how do you feel about this? They are moisture resistant and for bathrooms where they will be over OSB. On one sheet the crack is square to the edge of the sheet so much like how you'd join a sheet. On the other it's at a slight angle so may be no good. If using the one that's square, I could cut it clear and leave a small joint for the plaster skim.

BG give the guidance below when it comes to wall tiling. I presume an 11mm sheet of OSB counts as equivalent to a 12.5mm plasterboard and so it's OK to use 12.5mm over it?

Thanks this is all really helpful. So sounds like the winning recipe is: Studs at 400mm c/c (70mm C-studs in my case) OSB (in my case 11mm) onto studs, held 15mm off the floor screed 12.5mm moisture resistant plasterboard onto OSB, held 15mm off the floor screed Plaster skim (Thistle Multifinish or is there a better choice for bathrooms?) Tanking solution (any recommendations?) CT1 shower tray against the plastered wall and tile above as needed Elsewhere, use cementitious tile adhesive to fill the 15mm gap when tiling the floor

I've sat the 11mm OSB on offcuts of 11mm OSB so am a bit shy of the 15mm. I haven't fitted the plasterboard yet though so could try cutting 4mm off though could be tricky.

I was hoping for some tips on using OSB under plasterboard in bathroom walls. How far off the screed should the bottom of the OSB sit? Particularly next to the shower tray should I raise it clear of where the top of the shower tray will be and use either smaller OSB offcuts on the studs as packers or perhaps use 11mm thick timber there? Is it worth treating the bottom of the OSB with anything? How far off the screed is it normal to raise moisture resistant plasterboard? Note both of these are distance off screed not off top of tile. I plan to tank the plasterboard when done. Is that considered a good approach or will it create difficulties for tiling or plastering?

I'd be worried about having the 63x38 CLS studs that way round. The deflection under the same load is 2.7 times as much in that orientation and thickness in the line of the load force is king for keeping deflection down. 600mm centres compounds it further and makes it 4 times floppier than 400mm c/c with 63x38 CLS in the correct orientation. You'd probably be better without staggered studs and using resilient channel or think about using Metal C-studs (also Acoustic studs are an option there). Second Moment of Area: (63*38^3)/12 = 0.29E6 vs (38*63^3) / 12 = 0.79E6 -> 0.79E6 / 0.29E6 = 2.7 Beam deflection is inversely proportional to Second Moment of Area.

Here's what the return will look like in terms of OSB:

I wonder if I should have held the OSB a little higher than 10mm off the screed, but the plasterboard will need to come down about 5mm above the screed I presume.

I've gone with the stripwood approach. Hard to see, but I left a 3mm gap between the two boards by resting the top one on screws sat on the bottom one whilst installing. Also 3mm gap at the blockwork and will do he same at when I add the 15mm plasterboard continuation. I've not taken the OSB to the ceiling as that is 2.7m and there won't be cause for anything up there (will there?). I'll pack the studs at the top with stripwood and strips of OSB just at the studs. I raised the OSB about 10mm off the floor, you can see a strip of OSB under the sheet edge which I will then chop up and use as above. Stud positioning to avoid pipe penetrations is the next key thing. The sink waste is going into the wall 600mm room the RHS end of the OSB (400mm stud centres). It will then pop out in the bottom left corner and I expect I will need to pass water feeds in there too to then take to the sink and continue round, into the return and over the door in the return to the shower. The other route to the shower is along with the shower's waste, but I'd need to cut a trench into the screed for it to continue past the shower trap and onwards to the stud wall. [Note: the stud in the odd position is just moved temporarily

That doesn't work so well with the 1200mm gauge unfortunately