Mini expansion device for portable water

I've posted before about this - but I have new information.

I have not chosen a boiler yet, although Viessmann looks like a good contender.

Anyway, there are times in the winter where, if we say take a short holiday, my insurance says "turn the water off" - but I would like to leave the heating running.

Is this a problem (rhetorical):

Physically - if we've hydraulically locked both sets of our plumbing, a very small amount of expansion in the boiler's heat exchanger *could* result in a spike in pressure (copper pipes being not very elastic).

Well - Viessmann say no as they say the Vitodens combi has a small expansion vessel built in on the potable side in addition to the main one on the heating side.

But covering my bases in case I change my mind about the boiler, I looked at an old boiler manual of a boiler I had once:

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and on page 9 it says, on the right of the diagram, half way down:

"Note: If the mains is fitted with water meter, check valves or loose jumper stop c*ck, then a DHW expansion device must be fitted."

That clearly says to me that combi boilers should not have a hydraulic lock on the potable water circuit while they are running (unless the manufacturer has built in a safeguard like Viessmann).

Anyway, I see no harm in adding a small external one - it might help with water hammer anyway. But which one?

I see an american campany, Sioux Chief make the ones Toolstation sell:

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Does not say "WRAS" or "potable" but clearly its friend with the 3/4" threads on is designed to go on the cold mains near a washing machine. Checking further I think these things meet the equivalent USA version of WRAS. Neat, small and solid looking.

The other option is something like:

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Bit lumpy, but more volume.

Reply to
Tim Watts
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What sort of water is it:-)?

Reply to
ARW

Question: Is the hot water from a combi boiler always regarded as potable, or does it depend on the boiler?

Reply to
Graham.

I think so, but this goes on the cold side.

Reply to
Tim Watts

The usual - wet :)

And slightly hard, but not mentally so...

Reply to
Tim Watts

It's the cold hard icy stuff you need to worry about:-).

Does your insurance co really require you to turn off the water when you go on a short holiday? Such clauses about water and empty houses usually only apply when you leave the home empty for several months and then they often require a drain down of the CH.

Reply to
ARW

My current one does (or I would not bother) - and it's really stupid. I've seen other policies that say "turn off water OR leave the heating on low" which is a bit more sane.

This one is fascist enough to say "even if away for one night".

Reply to
Tim Watts

Portable - he's taking it on holiday!

Reply to
Roger Mills

FFS and water leaks cannot happen in the day time whilst you are at work?

Reply to
ARW

Care to name them, so I never make the mistake of buying one of their policies?

Reply to
Andy Burns

I read the manual for our new Worcester Bosch (much to the amusement then alarm of our plumber) and that said to put an expansion vessel on the cold side.

He had never heard of this before (!) but quickly obtained and fitted one.

Just been upstairs to have a quick look but there are no distinguishing marks on the front and I would have to empty the airing cupboard to get a really good look behind it.

So I conclude that such things are generally available in local plumbers merchants.

Somewhat confusing discussion here

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which suggest that not many people read the WB manual.

Cheers

Dave R

Reply to
David

The FAQ at

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say ok for potable ( I have one on our cold supply to loft tank)

Q: Are Sioux Chief water hammer arresters safe for potable water systems? A: All Sioux Chief water hammer arresters are safe for potable water systems. The dual o-ring piston is lubricated with FDA approved Dow Corning 111 silicone compound and all solder joints use lead-free solder. (see following note)

Safe Drinking Water Act/NSF Standard 61 According to the Safe Drinking Water Act (SDWA), it is unlawful to sell any plumbing fixture or fitting that is not ?lead-free? after August 6, 1998. In addition, ?endpoint? devices only (faucets, etc., defined by NSF 61, Section 9) are required to be certified to the NSF

61 Standard. All Sioux Chief products are considered ?in-line? devices (pipe, fittings, etc., defined by NSF 61, Sections 8 and 4) and meet the lead-free requirements for NSF 61 as defined by the SDWA and are not required to be certified to the NSF 61 Standard. Thus, all Sioux Chief products are acceptable to sell now and after August 6, 1998 since they meet the requirements of the Safe Drinking Water Act and NSF 61

Slighty different (rubber diaphagm) to the spring loaded Sioux- we also have similar device, WRAS approved, from BES (Mini Expansion Vessel

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after our main stopcock to reduce the water hammer we get from next door...

Reply to
Geo

Oh bollocks... Mr PissedFingerz strikes again...

Reply to
Tim Watts

Yeah - that's what I think. But you know those bastards are looking for any excuse to not pay out.

I generally like AXA as they have the least stupid conditions - but I have an open building notice, and that's limiting the choice of insurers. As it happens the current insurer is at least able to understand that it's possible to have a habitable and secure building with an open BNA - because the remaining items are:

1) Finish electrics (as in add remaining circuits); 2) Add remaining 25% of thermal insulation; 3) Connect and commission the second bog (drains aspect); 1+3 are aimed for this year - and 2 might be next year as it's actually quite a lot of grunt work and has some pre-requistites.

But I sure will be glad when I get the completion cert - it's been a long old haul, this house.

Of course, if I'd done this in, say, the year 2000, I would already have the completion cert because the remaining items (maybe except the bog) would not be a part of it.

One thing is for sure - when I get the cert, I am never opening another BNA!

Reply to
Tim Watts

See my other post - they do have some good points..

Reply to
Tim Watts

What's it look like? Is it more like the Toolsatan mini-rester or the one that looks like a tiny but perfectly formed normal expansion vessel?

Interesting that WB require one - they are my other choice of boiler.

I am trying to work out whether they are actually of value or not:

1) If the heat exchanger did get hot with a hydraulically locked all copper system, it might just cause enough of a pressure spike to crack something. 2) OTOH I think most boilers will not actually send primary water to the heat exchanger unless the flow switch detects flow, which will not happen if the stop c*ck is off. More likely to expreience a partial vacuum as the heat exchanged cools down if it was hot when you turned the c*ck off. And that's only going to subject the system to -1bar or so. 3) There's probably enough give in a normal system anyway just by virtue of having a washing machine hose present (being rubber it can expand a bit).

OTOOH the manufacturer says do it and there's not real harm in doing so

- in fact it might do a bit of good with water hammer.

I am not surprised plumbers have not heard of it - they never read the installation manuals anyway!

Reply to
Tim Watts

Thank you - Sioux Chief it is on form factor alone. I don't actually care if it has not been officially certified for the UK - if it's lead free and suitable for potable water in the US, that's good enough.

Interesting the yanks have gone "lead free" on the books too.

Reply to
Tim Watts

Oh - one thing:

I assume an american 3/4" thread is compatible with BSP? Or am I going to need a weird female joint to mate it to?

Reply to
Tim Watts

Standard - 1/2" male thread.

Reply to
Geo

Oh of course - the non inline is 1/2" - but thanks for confirming it's "standard". You cannot tell with the merkins as they have invented all manner of "imperial" threads as have the Brits.

Reply to
Tim Watts

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