Secondary return or trace heating tape?

Bendy_House

If you are considering gaining access to the existing pipe in order to trace-wrap it, or even add a secondary return, surely running an 8 or 10mm pipe alongside it will be just as easy, if not more so?*

Have I mentioned that Grumb has almost certainly come up with the perfect solution in your case?

*Re-reading your first post, there isn't a supply pipe from the loft to the kitchen at the moment? So the plumber has yet to actually install a pipe of any size?

I have to ask - why (seemingly) aren't you delighted and relieved by the narrow-pipe idea/solution?

Chickereeeee

Bendy_House said:

If you are considering gaining access to the existing pipe in order to trace-wrap it, or even add a secondary return, surely running an 8 or 10mm pipe alongside it will be justt as easy, if not more so?*

Have I mentioned that Grumb has almost certainly come up with the perfect solution in your case?

*Re-reading your first post, there isn't a supply pipe from the loft to the kitchen at the moment? So the plumber has yet to actually install a pipe of any size?

I have to ask - why (seemingly) aren't you delighted and relieved by the narrow-pipe idea/solution?

The cylinder is currently in the kitchen, with maybe 5m run of 15mm pipe behind the cabinets to the tap. Hot water comes through reasonably quickly. Relocating the tank to the loft adds maybe another 5m to the run. Current cold feed in the kitchen will have to be taken to the loft. 

Now, my thinking is, trace heating tape would only have to heat the new part of the pipe (the additional 5m), as would the secondary return. I am not  sure if the small pipe approach would require the whole 10m of pipe  to be small bore or not.

Anyhow, I will chat to plumber and see what he says. 

Bendy_House

Chickereeeee said:

The cylinder is currently in the kitchen, with maybe 5m run of 15mm pipe behind the cabinets to the tap. Hot water comes through reasonably quickly. Relocating the tank to the loft adds maybe another 5m to the run. Current cold feed in the kitchen will have to be taken to the loft. 

Now, my thinking is, trace heating tape would only have to heat the new part of the pipe (the additional 5m), as would the secondary return. I am not  sure if the small pipe approach would require the whole 10m of pipe  to be small bore or not.

Anyhow, I will chat to plumber and see what he says. 

10mm pipe has less than half the volume of 15mm pipe. So you can double the length in 10mm with no increase in the water volume that needs shifting to your kitchen tap and appliances. Ie, 10m in 10mm won't be worse than your current 5m in 15mm (gravity not yet taken into account...).

8mm pipe has less than a third of the volume, so super-ditto - ie, hot water should get through 10m significantly faster than your current setup. Provided, of course, the same, or adequate, volume of water can be shifted through the narrower pipes.

Will it work? Almost certainly, yes.

You currently have more than 3 bar pressure at ground level? You can make that 3 bar at loft level simply by moving the PRV up there, just before it feeds the unvented cylinder. (I would suggest that this is actually not at all necessary, but I'm just saying it can be done). I would then hazard that any friction loss in even an 8mm pipe would be petty much fully countered by the gravitational pull from loft down to t'kitchen.

If Grumb's idea doesn't work, I'll eat my hat. And offer to run to t'loft to bring down buckets of hot water for you.

I'll also hazard that your plumber will say 'No' to this idea.

Will it work? Yes. Is it the best idea since sliced bread? Yup. Am I p'ed that Grumb came up with it? Certainly. Will a plumber agree to it? Hmmmm.

Chickereeeee

It's not a new idea though:
https://forum.buildhub.org.uk/topic/597-10mm-hot-and-cold-pipe-runs-vs-15mm/

Bendy_House

Chickereeeee said:

It's not a new idea though:
https://forum.buildhub.org.uk/topic/597-10mm-hot-and-cold-pipe-runs-vs-15mm/

Gulp. Are you going to tell Grumb, or shall I?

grumbler

Damn! I was going to patent it 

Bendy_House

Hundredsofthousands of folk have had the same idea at some point.

Only one on this forum, tho'...