Waste pipework diameters and connections

[Olf]

Following @Nickfromwales advice I started with 50mm pipes for shower and sink, but what advantage (in performance) will they give me for manifold drain and UVC?

Being at UVC, will I be able to drain into common stack (made of uPVC), or do I relly have to think about a separate through the wall discharge point?

Here is the schematic, the spaghetti junction under the toilet is just boss pipe linking all the 50mm branches, one of those with 2 x knees to adjust angle to suit.

Edit: do I need a trap for washing machine, or a sealed connection will do?

Edit 2: AAV is missing! Will it be happy in UVC cupboard?

 

 

 

 

[Olf]

I think I can remove the UFH drain branch - for the rare (I hope) moments it is needed I'll ask washing machine to share both supply and drain.

[Russell griffiths]

You need a trap for the washing machine, sealing the waste pipe on just let’s the smells out of the drum. 

[Olf]

I'm on a version n+1 of the layout, basically everything mirrored, so all the connections can be done inside the new stud wall, rather than by chasing existing cast concrete.

This though moved UVC location and access and now the drain from relief valves is a bit harder to set up. Incidentally the main 110mm pipe will be running right underneath:

My idea is to come out with equal junction and then 110 to 50 or 32 mm reducer, but I'm missing here some trap, and one that wil be capable of accepting boiling water should temperature relief got activated. Any ideas?

[ProDave]

A waterless trap and the pipework should be ABS, not PVC, to withstand the potentially boiling water discharging from the UVC

[PeterW]

44 minutes ago, ProDave said:

A waterless trap and the pipework should be ABS, not PVC, to withstand the potentially boiling water discharging from the UVC

That’s not entirely correct. You can use polypropylene but it has to be BS / EN marked to the correct spec. What is sold as solvent weld pipe is not sometimes true ABS so you need to check carefully. 
 

@Olf why the UFH manifold drain ..? Never used one, it’s a hosepipe job normally ..!

[Olf]

14 hours ago, PeterW said:

why the UFH manifold drain ..? Never used one, it’s a hosepipe job normally ..!

That was just a folly, on the second thought got rid of it

 

I found an NHBC guidance that suggest:

'The discharge pipe and fittings should normally be metal. Alternatively polypropylene pipes and fittings, as described below, are an acceptable alternative material.
Polypropylene pipes and fittings should be marked to either BS 5254 ‘Specification for Polypropylene waste pipe and fittings’ or BS EN 1451-1 ‘Plastic piping systems for soil and waste discharge (low and high temperature) within the building structure’. The pipe should be marked with the following at max 1M intervals'

 

Need to check if I can find such certified 110mm waste pipe.

 

They use standard tundish and waterless trap, I'm plannig to simplify by using Hotun

 

 

[Olf]

Floplast say:

' Working Temperature:
Soil and Waste systems may be used to carry liquids when subjected to a continuous flow, with a maximum temperature of 76°C. Intermittent discharges of up to 100°C may occur, provided that a duration of less than two minutes is observed. '

 

I think I'm overreacting: with UVC fed indirectly from boiler (and later ASHP) and immersion heating only used to scavange excess PV generation or as a backup, chances of temeprature reaching level to cause escape of boiling water are essentially zero.

And should that ever happen, I may possibly have bigger problem than worrying if the pipework was happy with such a surprise.