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Author Topic: Hot water feed ?  (Read 359 times)
catfordbags
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« on: July 16, 2017, 12:05:07 PM »

Hi All ... starting to think about plumbing ... our GSHP is soon to be installed with an unvented tank ... should the hot water plumbing to the bathroom and kitchen be 22mm or 15mm ?  Looked it up online and it is one of those questions where people are split down the middle. Any wise words from navitroners ? Help would very much be appreciated.
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rogeriko
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« Reply #1 on: July 16, 2017, 12:11:42 PM »

The bigger the pipe the longer you have to wait for the hot water to come through and the more heat you waste left in the hot pipe when you turn the tap off. A pressurised system at 3 bar will deliver all you need at 15mm. Run one 22mm pipe just to the bath so it fills quicker if you have a high flow bathtap.
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eabadger
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« Reply #2 on: July 16, 2017, 12:33:37 PM »

15mm is what i used over all house, but have fed each of the 5 bathrooms seperetly from a 1" manifold on the cylinder, also manifold has taps so each hot supply can be shut down to do work, done the same for the cold and the radiators and glad of it.
other than run to kitchen which is +20m no issues with heat loss or pressure drop, but water over here at mega pressure especially overnight.

steve
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djh
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« Reply #3 on: July 16, 2017, 01:50:09 PM »

We did ours entirely in 15 mm layflat pipe, including the bath. All manifolded with a single run to each room where there are taps. And service valves on each run as well as at the appliances. My plumber made the manifolds from copper fittings rather than buying pre-made ones. It all works fine.

We do get some interaction on the hot supply to thermostatic showers between the pump on the thermal store starting up and the thermostats in the showers overcompensating, but that's nothing to do with the pipe runs. When replacement time comes, I'll fit fast-acting electronic showers rather than traditional mechanical ones.
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eabadger
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« Reply #4 on: July 16, 2017, 02:23:53 PM »

our manifolds, ignore the metric sizes, all pumbing is imperial here, just marked in metric, this one is 3/4 in out on straight to 1/2 above the taps.
https://www.bricoman.fr/collecteur-monobloc-avec-vannes-5-sorties-male-femelle-20-27-sorties-male-15-21.html


steve
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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
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« Reply #5 on: July 16, 2017, 04:59:23 PM »

Another vote for 15mm here your mains pressure will easily provide enough flow so that the difference in pipe size will not be noticable, I would also use plastic pipe such as Hep2O or similar, less heat loss and nice and quiet too.

Desp
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eabadger
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« Reply #6 on: July 16, 2017, 05:56:14 PM »

hep20  pipe Grin
but speedfit fittings

steve
« Last Edit: July 16, 2017, 05:58:00 PM by eabadger » Logged

1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
Countrypaul
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« Reply #7 on: July 16, 2017, 07:53:49 PM »

We've just used plastic pipe (JG speedfit) but since many of the fittings were a good distance from the thermal store we have used a 22mm supply pipe with 15mm drops to each basin/shower/sink/washer/etc. We have put in a 15mm return so that we can have a recirculator in future if we feel it necessary. We considered a manifold approach but decided against it since we would end up with 6 sets of 15m pipe in parallel for most of the distance plus a 22mm for the bath. The supply to the WCs has been run in 15mm plastic (polyplumb grey) to distinguish it easily as I plan on changing that to a rainwater supply in future.  Copper 28mm has been used for the WBS and a number of fittings on the thermal store (eg. vent plus F&E tank pipes etc., along with take offs from the tank to the TMVs) but plastic for everything we could.   
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djh
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« Reply #8 on: July 16, 2017, 09:44:47 PM »

The supply to the WCs has been run in 15mm plastic (polyplumb grey) to distinguish it easily as I plan on changing that to a rainwater supply in future.

That doesn't do it. It has to be marked with green bands etc. And the plumbing then has to be inspected, IIRC. Check the regs.
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eabadger
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« Reply #9 on: July 17, 2017, 08:42:07 AM »

regs? inspection? is this a new build?
is this what bco's look for? i am amazed especially after reading that those cladding panels on those flats were passed by bco.
i thought you could do diy plumbing still, has this been banned?

steve
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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
djh
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« Reply #10 on: July 17, 2017, 05:44:37 PM »

i thought you could do diy plumbing still, has this been banned?

No, you can still DIY but you then face more inspections, by the water supplier, not the BCO. Duly authorized plumbers can self-certify the installation.
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Cheers, Dave
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