Stick with 15mm pipe or use 10mm?

[Pete]

When I poured the slab (Passive) I put two 15mm pipes in for the H&C for the island unit. Due to a change in layout of the island unit I still need the pipes but they need to be longer so I either put in some 15mm straight connectors and continue the 15mm pipe or I can push through some 10mm inside the 15mm pipe that I already laid in the slab and have one continuous pipe right through to the base unit that will have the boiling water tap and tee for the DW so avoiding a connection under the island unit. I am doing a manifold system for the H &C system thus avoiding connections in inaccessible places so being anal what do I do. No great problem just be interested to see what people would do? TIA

[Jeremy Harris]

10mm should be fine for a run to a sink.  I've noticed that French plumbing often seems to use much smaller pipe than we do, around 10mm or so seems normal for basin and sink pipes, and they seem to work OK.

 

The pipe that runs from our boiling water unit up to the tap is really small, around 5mm bore, yet that works just fine (in fact we've had to turn the flow rate on it down a bit).  The same goes for the flexis that feed mixer taps, they only seem to have a bore that's around 6mm or so, yet work just fine.  I have a feeling that we tend to use large pipes just because historically houses had low pressure hot and cold systems, fed from a tank in the loft.

[Russell griffiths]

How far a push is it??

i would be interested to see you push 10 mm up 15mm I may be wrong but the first m will be a doddle, the others may not be so much fun as friction kicks in. 

 

Go on prove me wrong. 

[Gone West]

16 minutes ago, Pete said:

or I can push through some 10mm inside the 15mm pipe

How easily does 10mm pipe push through 15mm pipe?

[Pete]

1 minute ago, Russell griffiths said:

How far a push is it??

i would be interested to see you push 10 mm up 15mm I may be wrong but the first m will be a doddle, the others may not be so much fun as friction kicks in. 

 

Go on prove me wrong. 

Watch this space

 

1 minute ago, PeterStarck said:

How easily does 10mm pipe push through 15mm pipe?

It has to travel about 1.5m so a bit of silicone spray and we should be ok

[Russell griffiths]

Pah 1.5m that’s just a boys distance, not even worth a bet. 

[Carrerahill]

33 minutes ago, Pete said:

When I poured the slab (Passive) I put two 15mm pipes in for the H&C for the island unit. Due to a change in layout of the island unit I still need the pipes but they need to be longer so I either put in some 15mm straight connectors and continue the 15mm pipe or I can push through some 10mm inside the 15mm pipe that I already laid in the slab and have one continuous pipe right through to the base unit that will have the boiling water tap and tee for the DW so avoiding a connection under the island unit. I am doing a manifold system for the H &C system thus avoiding connections in inaccessible places so being anal what do I do. No great problem just be interested to see what people would do? TIA

 

If it was me, I think I would need to do an experiment first, at least on the main cold feed for the sink tap  -  copper tap connector tails are all 10mm pipe which get event smaller as the taper at the tap itself, but the whole run on 10mm - I am keen to confirm this as I have 100m of copper 10mm on a coil that I could then use to run H&C to my new kitchen with no need for any joints until under the sink all the way from the main stop-cock - now that would be nice! I suppose you can do the same with 15mm plastic but I won't have plastic pipe anywhere near my house. Copper all the way. The only exception would be small bits of heating pipe.

 

 

[joe90]

I have run all my hot pipes to sink taps in 10mm to cut down on time to receive hot water and the pressure is far better than I expected.