I need a funny shaped header tank for a vented system. It will probably have to be long and thin to fit in the space below the ridge of the roof. How feasible is it to build one? I was thinking of asking a fabricator to build a box out of stainless steel. Is it straightforward to make copper connections to the box?

The other query was insulating it. It should not get too hot, but it would be sensible to have some insulation. I've seen these spray on foam companies. Might this work? Might there be a better solution?

I'd be grateful for any comments!

About 200 litres / 250kg / on steel superstructure, probably using a timber stand of some sort.

Nice idea! It would need to be heatproof in case the system overheated, and the space is really limited. A long (2m) cylindrical container would be good, but not quite the ideal shape, and quite expensive. I think the best solution will be to get one made.

Get one welded up by a steel fabricator. IMO stainless steel is not necessary after all radiators are not stainless ! Connections are easy, you just get the fabricator to weld in iron pipe fittings where you want the connections. If you want a ball valve in it then you will need an open top otherwise it can be closed, but must have an open vent hole and either way it should have an overflow (usually led out to a gutter or just poking out of the wall. It must be insulated if it is in an unheated space and either EPS (but think about feeding the mice) or glass wool or what ever else you care to use that might be more expensive but have more eco-bling. If the space beneath the tank is heated then build and insulation box around the tank so as to include the tank in the heated envelope. Don't forget to insulate the pipes up to the tank if the space is unheated.

Plastic is not a good idea for a header tank because if the heating goes pear shaped then the header tank can go all soft and wobbly and then sag and leak.

Thanks @Peter, that's just what I wanted to hear. What sort of thickness do you think I should specify for the sheet?

Posted By: ComeOnPilgrimI think I'll need something that is about 2000 mm long, and a funny shape (see attached).

well, you could get *THAT* shape done by a boat-builder !
(looks just like a ... Water Tank !)


cf. https://www.google.fr/search?q=water+tank+stainless+sailboat&client=firefox-b&tbm=isch&imgil=Qsccjyo3PHNJDM%253A%253B50x8GbDVHLU2NM%253Bhttps%25253A%25252F%25252Fwww.westmarine.com%25252Fwater-heaters&source=iu&pf=m&fir=Qsccjyo3PHNJDM%253A%252C50x8GbDVHLU2NM%252C_&usg=__iEafKlcWnPRwiyhHueihy00Acgc%3D&biw=1024&bih=641&ved=0ahUKEwjW0NGPqNLSAhWIzRQKHc-eDiQQyjcIKQ&ei=tfPFWJaiH4ibU8-9uqAC#imgrc=ILw9ii2xygz7iM:

gg

Is this a "Feed and Expansion" tank? I had a SS one made for my back boiler it's nowhere near as big. Cold feed at one end and overflow at the other.

It has to go somewhere that it is visible/noticeable. Outside is most normal and conventional because water falling down the outside of a building is noticeable. Mine goes to a tundish alongside the tank and thence to the nearest soil pipe because I didn't want any extra penetrations through my walls, especially not open pipes!

As long as the tundish is somewhere it can be seen and heard, you should be fine. FWIW, my 'approved' plumber went along with it and signed it off and he then used my site for part of his regular certification appraisal so I'm fairly sure it is kosher.

@goodevans, I was going to have a manual fill, but presumably you also need an overflow for if the tank boils.

Posted By: goodevansThere is an alternative of having a manual fill header tank (tap nearby and a hose).

That was my original plan, but my plumber said such an arrangement was more of a nuisance than a ballcock and I went with his suggestion. It's too early to say whether he was right - we haven't had any problems yet.

Posted By: djhAs long as the tundish is somewhere it can be seen and heard, you should be fine. FWIW, my 'approved' plumber went along with it and signed it off and he then used my site for part of his regular certification appraisal so I'm fairly sure it is kosher.

Hi @djh, can you provide more details on this? I essentially did the same, but a plumber I asked for advice on central heating controls looked at it, laughed, and said it had to go outside rather than into (eventually) a plastic soil pipe. To be fair, he was exceedingly patronising, and hasn't got back to me with any advice on controls, but I thought I had better check that I had it right.

This might be off the point, but FWIW, I have seen a case of a safety valve from a normal HW cylinder, venting directly into a 32-mm grey PVC drain pipe in turn connected to a handbasin drain in adjacent toilet.

The cylinder pipe first traverses a poured-concrete (loadbearing) wall, 140mm thick. During construction, no pipe sleeve was employed. After some years, the amount of water damage in the adjacent WC was *extreme*.

gg

saturated wall: rising damp to over a meter high, wall surface exploded (blistered paintwork), damage to built-in cupboard.

I have a photograph of it, somewhere on my currently unavailable hard drive...

gg

Apologies for the overly summary description.

During construction (1993), the overflow from the HW cylinder was routed into the drain pipe of a washsbasin in the neighbouring water closet. A concrete wall was then poured around the (horizontal) PVC drainpipe from the T&P valve, but no pipe sleeve was used.

As the concrete shrank, the pressure deteriorated the wall of the PVC pipe.

Regular dumping of (very...) hot water from the HW cylinder overflow exacerbated the problem in that the water penetrated through the PVC pipe, resulting in saturation of the concrete wall.

In the meantime the appartment was let out and the tenant reacted like an ordinary tenant, i.e. said nothing until the decoration in the WC was very far-gone. The estate agent "had the damage repaired" but the problem persisted until the owner took control and had an insurance claim: the solution involved breaking out the through-wall pipe, and fitting a sleeve with a copper pipe and correct slope, into the (same) washbasin drain.

Moral of the story:
a HW cylinder vent valve should not be incorrectly plumbed into internal PVC plumbing...

cf.

www.watts.com/pages/support/tp.asp?catId=64

"Warning: The discharge from a T&P valve can be very hot. It is very important that all T&P valves be installed properly with a discharge line piped downward to an adequate drain to avoid property damage and to minimize possible human contact (...)"

Don't know if this helps any.

BTW, all remaining 150-odd properties in the same development were plumbed the same way...

gg