Any plumbers in Da Haus?

[mangocrazy]

In France I have a woodburning stove with back boiler that I'm in the process of fitting and doing pipework for. The stove will heat hot water in the cylinder and run up to 5 radiators. The dealer insisted that all pipework should be 28mm up to the cylinder/rads, but the inlet tappings on the DHW cylinder are only a paltry 14mm, so I have to reduce from 28mm to 14mm. I was thinking of going 28 => 22 => 18 => 14 but was wondering whether its' best to stagger the reductions over a few metres, or just bang them in one after the other in rapid sequence.

Does it make any difference or am I worrying about nothing?

[Count Steer]

<wet finger in air>I'd guess that the shorter the length of smaller bore pipe, the better in terms of lower system pressure</wfia>

[mangocrazy]

Yes, good point. The only thing I was thinking of is that a bore reduction will result in turbulence in the flow. Is it best to get it all out of the way quickly, or allow the flow to settle down between reduction points?

[Count Steer]

Yes, good point. The only thing I was thinking of is that a bore reduction will result in turbulence in the flow. Is it best to get it all out of the way quickly, or allow the flow to settle down between reduction points?

Looking at a towel rail here they have stepped down in 2 steps in the last few inches before the rail. It's a bit of an eyesore tbh. If you can get a 28-14mm coupling I'd go with that I think. Fewer possibilities for leaks, neater. If there are problems you can revert to plan B more easily than going the other way.

Disclaimer: Not a plumber.

[Mussels]

If you struggle to find the right adapter then the answer may be to drill out a 28mm cap and solder some 14mm pipe to it.
I realise it's France but 14mm sounds odd, could it be 15mm?

[MingtheMerciless]

Just googled, they use 14mm copper pipe, amongst others.

[mangocrazy]

Plumbing sizes in France are different to the UK (unsurprisingly). 22mm copper is about the biggest you see here, then 18mm is the next size down, then 16, 14, 12, 10 and even 8! Wall thickness is 1mm. so 14mm copper will fit inside 16mm copper and you don't need an adapter. I've either got or can get all the step down sizes I need, but it's just whether to do a 'fast reduce' or a slow one.

Price of copper tube over here seems to be much more expensive than the UK, so I've brought stocks of 28, 22 and 15mm copper and fittings. If I use a swaging tool on 15mm copper I can get 14mm French copper to fit inside, so I can mix and match UK and French pipe.

[Silly Car]

One of the reasons UK copper pipe may be cheaper, other than the tanking pound, is British Standard pipe is 0.7mm walled so 30% less material. Interestingly though (or not), 1mm walled copper pipe bends with far less likelihood of wrinkling than BS pipe.*


* I boringly watch a YouTube clip about it the other evening.

[MrLongbeard]

* I boringly watch a YouTube clip about it the other evening.

And people tell me I need to get out more

Although I watched vids about bear guns and treadmill cranes yesterday

[Bowman]

In France I have a woodburning stove with back boiler that I'm in the process of fitting and doing pipework for. The stove will heat hot water in the cylinder and run up to 5 radiators. The dealer insisted that all pipework should be 28mm up to the cylinder/rads, but the inlet tappings on the DHW cylinder are only a paltry 14mm, so I have to reduce from 28mm to 14mm. I was thinking of going 28 => 22 => 18 => 14 but was wondering whether its' best to stagger the reductions over a few metres, or just bang them in one after the other in rapid sequence.

Does it make any difference or am I worrying about nothing?

The tappings into the cylinder sound extremely small. Is it an indirect cylinder? Are the flow and return gravity or pumped?
I'm not up on French plumbing but something doesn't seem quite right with that setup.

[Kneerly Down]

Presume the 28mm is needed if it's not pumped. If you put a pump in the circuit I would have thought you could go with the smaller bore pipe. My inlaws used microbore for their central heating circuit for a big old 7 bed house and seemed to work well.

[demographic]

From memory I heard that its recommended to use large diameter pipes from backboilers to the hot water tank because below a certain diameter the thermosyphon doesnt really...erm...thermosyphon so well and you can boil the water in the backboiler.

Dunno what sizes they are but I guess it all depends on lengths of run and a number of other factors.
Might give you something to use as search criteria though.

[mangocrazy]

Well, it's done now and I'm back home in Blighty. I used 28mm up until about half a metre away from the cylinder when I stepped down to 15mm , as it was easier to make the routing in small diameter pipe (the cylinder is quite close to a wall and there's no direct line of sight to the take-offs). Then I stepped down from 15mm to 14mm at the cylinder.

In an ideal world I'd have taken the 14mm fitting on the cylinder off and found a 22mm tapping underneath, but when I tried to undo the 14mm tapping on the cylinder it didn't budge even after some fairly heavy persuasion, so I bottled it and left it at 14mm, and the associated steps down. Here's a pic of how I left it:

Cylinder_plumbing.jpg (310.09 KiB) Viewed 115 times

And this is a section I added while I was there:

Copper_spaghetti.jpg (409.96 KiB) Viewed 115 times