Efficient Hot Water Piping

[NeilW]

Somewhat American, but interesting nonetheless.

 

http://www.garykleinassociates.com/PDFs/15 - Efficient Hot-Water Piping-JLC.pdf

[joe90]

Yup, that’s why I installed a manifold and 10mm pipework for hot taps ( but not for showers and bath) in single plastic runs with very few 90’ bends.

Edited March 8, 2018 by joe90

[epsilonGreedy]

10 minutes ago, joe90 said:

Yup, that’s why I installed a manifold and 10mm pipework for hot taps ( but not for showers and bath) in single plastic runs with very few 90’ bends.

 

 

Most of that document went over my head though I noted in the performance section the manifold implementation was ranked poorly, something to do with the geography of the house maybe?

 

I need to get my head around how HW circulation pumps work... so much to learn.

[joe90]

Regards the manifold in my build, it’s next to the DHW tank and central to the two bathrooms and kitchen so any pipe runs are as short as possible. Just re read it and it talks about 334ft of pipe with a manifold, I recon mine is less than 50ft ?

Edited March 8, 2018 by joe90

[PeterW]

My longest hot run is 7m to the kitchen tap, 6m to the utility. Bathrooms are both less than 5m. It’s not difficult if you plan it - I’ve not used a manifold but each section has its own isolators in the tank room. 

[Onoff]

I'm going to measure all my pipe runs just to make you all feel BETTER. I bet I've got the longest!

[ProDave]

2 hours ago, Onoff said:

I'm going to measure all my pipe runs just to make you all feel BETTER. I bet I've got the longest!

I doubt it

 

I wired a house just over a year ago, easily twice the size of mine. The Hot water tank was in the plant room at the opposite corner of the house to the kitchen. There must have been 20 metres or probably more for the hot water to get from the tank to the kitchen tap.

 

This was a plumbers house by the way.

[lizzie]

My wetroom is at the absolutely furthest away part of the house from the tank...not measured but I would guess at  min 20 metres.. Running water in the basin in there for cleaning yesterday and it took an age for hot to come, not tried the shower yet..........pressure seemed ok in the tap.

[Bitpipe]

22 minutes ago, lizzie said:

My wetroom is at the absolutely furthest away part of the house from the tank...not measured but I would guess at  min 20 metres.. Running water in the basin in there for cleaning yesterday and it took an age for hot to come, not tried the shower yet..........pressure seemed ok in the tap.

 

Problem is you have a long 'dead leg' to the wet room and when you turn off the tap, the water in the pipe goes cold - you then need to draw off this cold water before the hot arrives from the tank. Pressure is not the issue.

 

Based on learnings here (or eBuild) we knew to spec a return loop - effectively the hot water supply loops around the house and back to the tank driven by a pump. Each bath/shower/tap then branches off this so the dead leg distance is minimised. The manifold approach is an alternative design to get the same result (will let the more qualified discuss the differences).

 

Our hot water return pump could have been driven by a pipe stat & timer (as plumber originally suggested) but we connected it to the same circuit that drives the MVHR boost which is activated either by turning on a bathroom light or by a PIR in each bathroom (for daytime). So walking into the bathroom starts the pump and ensures that there is hot water close to the tap when you need it - only a few seconds for it to come through.

[Plumbersmateuk]

11 minutes ago, Bitpipe said:

So walking into the bathroom starts the pump

I want to go down one of these routes,

 

13 minutes ago, Bitpipe said:

(will let the more qualified discuss the differences).

Most grateful if it hasn't been discussed already

[Bitpipe]

2 hours ago, Plumbersmateuk said:

I want to go down one of these routes,

 

I asked my sparky how he achieved it and he said thus:

 

The switches and PIRs are basically just wired in parallel, the boost connections only usually give you the switching pair but the PIRs require a neutral so picked that up from the MVHR unit and then wired the whole lot by daisy chaining between each point with 3 core & earth with the neutral just connected through (separately to the local lighting neutral to avoid RCD tripping) in each conventional switch. The switches are double pole switches so that the local light switching is in one side of the switch and the MVHR boost in the other