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Discuss DIY manifold with PEX and plumbing a bathroom in the Plumbing Forum | Plumbing Advice area at

Hello all, my wife and I have recently purchased a house in Edinburgh (move in date 6th dec hopefully) and I have been working hard to get a plan done for a diy manifold and I shall do a complete refit of the bathroom. I plan to do it all myself bar the electrics and boiler connections. The floor is 2m x 2m.

The boiler is a combination boiler but unsure if it is a condensing type or not. It is around 10 years old as informed from the owner. Don't have a pic or access unfortunately till the 6th. Located on the ground floor and serves the ground floor kitchen, 1st floor bathroom and the radiators on both of those floors. I plan to do the bathroom to begin with and want to put in underfloor heating along with a towel radiator on the hot water line so it runs all year round. Im getting a bit confused with the towel rad and UFH, will i need a 4 way mixing valve on both the towel rad and UFH, im sure there is a better way.

It not complete yet but I have attached a PDF with lots of drawing and sizes etc and was just hoping for some feedback. It is missing the electrics, central heating and drainage so far. Lots of pipes to move to correct location!

Page 1: is the most important for me to get correct, it will help the rest fall into place. All the 3d parts are just rough.

Is the filling loop usually just a valve kept in the off position or should it be something else?

Are the expansion tanks locations correct in the drawing? I dont know if there is an expansion tank inside the boiler or not, will have to wait and see.

Page 2: I am interested in making the manifold system which is constructed from 22mm copper leading onto pex connections for all pipework throughout the home. 22mm for DW, WM shower and hoses. 15mm for the rest, including central heating. Have put a shutoff valve and drainage for each line.

Page 3, 4 and 5:
general idea of plumbing in 3d.

Page 6: wetroom floor cross section, shows the layers of ply, Ditra membrane and adhesives. Is my porcelain tile adhesive a good choice, going to grab it from Stax for a better deal!

Page 7:
Im going to go through studs as much as possible with piping but sometimes will need to go through the joists. Want to check my locations are ok.

Thanks for reading and will try to reply asap but have a needy toddler in the house to look after!


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