Fitting a new cold water tank

[jkn]

Hi All it looks like our old cold water tank is leaking in the loft. I have got a drip tray under it and will be investigating further, but there is at least a possibility that a new tank will be needed.

To give an idea of the vintage etc. the houss is around 1950s I think, and the old tank seems to be at least partially made of zinc-covered sheet construction, with some soft of compressed straw boards for insulation.

I will be measuring up the old tank properly but I'm guessing it's

50 gallon, maybe a little bigger.

Is there anything I should particularly need to know when considering replacing this myself? I am hoping to be able to not modify any of the piping, and to cut holes in the new tank to match the old. Am I being delusional?

Thanks Jon N

[charles]

or in the case of our house, before the roof was fitted. Mind you, modern plastic tanks are flexible and will go through quite small gaps.

[DerbyBorn]

Make sure you have a suitable surface to put it on that will spread the load.

[Dave Liquorice]

A galavnised iron tank will heavy even when empty. It was probably installed before roof and/or ceilings were in place, the loft hatch may be to small. So either you just drag it out of the way and leave it or cut it up, very hard work by hand, very noisey by machine be that a jigsaw with metal cutting blade or angle grinder (watch were the sparks are going...).

A plastic tank will require firm well supported and solid base. 22 mm code 3 (I think that is the water proof grade) OSB or maybe 18 mm WBP ply.

If you don't have to modify the pipework, watch out for the pink flying elephants...

[Brian Gaff]

Can you get the old tank out of the loft? I could not so ended up with two smaller tanks instead. Ours went till the late 60s from 1939, and was galvanised steel with what looked like rivets. I could have got somebody in to cut it up and remove it but so many people had done this and nearly burned down their houses I left it up there. Apparently according to an old bloke who was around at the time the houses were put up the tanks were put in before they made the roofs, then the hatch to the loft was made just too small to get it out. So you see daftness is not a new phenomenon! Brian

[Bob Minchin]

Your pipe work may be iron threaded stuff which could well be corroded to the extent making it difficult to reseal old fittings or if copper, will be imperial sizes. If you have to change any fittings then 1/2 and

15mm pipe will usually fit OK into compression fittings but 22mm/3/4" does NOT so you will need conversion olives to replace the standard ones in new compression fittings. The conversion olives are often marked in green. of you are soldering you can get conversion straight couplers for 3/4-22mm. 1/2"-15mm solder might be a bit tight - I can recall which is slightly bigger of the sizes. For your info. Imperial pipe was sized on the bore and metric is sized on the OD.

[Dave Plowman (News)]

I'd say it would be very difficult indeed to cut the new holes to match the old pipework perfectly.

Easier to make sure you have the bits needed to modify the pipework before starting. Basically, all new from the tank to a convenient place to joint to the old.

[ARW]

You can with an angle grinder.

[GB]

I understand. The sparks from the angle grinder set fire to the roof, thus creating a nice big hole to get the tank out of.

[charles]

In our previous house - over 40 years ago, therefore - I used a jig saw. Less sparks than an angle grinder, so less fire risk.

[jkn]

Hi All Thanks a lot for all of the useful info. I have learned a lot and been able to check some more details. In no particular order:

- I appreciate that the tank will need strong support. The current one is lifted up on a strong (4x2 or so) table. The top is slatted, so it looks like I will have to put some WPB on top to support the plastic tank.

- The measurements of the old tank are very close to those of the Polytank 25Gallon tank - it looks like that is the replacement to go with. I am pretty sure this will go through the access hole.

- I appreciate all the comments about having to cut the old tank up, or leaving up there etc. I will probably leave it up in the loft to begin with, to await a rainy day...

- The inlet and outlet pipes are copper, at least some are 28mm I think. I am now resigned to having to rework the pipework at least a little. I will spend some time working out any change in layout and what fittings this might need. I guess I want to be doubly sure that I have everything in place before setting out on this work, I don't want to be a washer short on a Sunday afternoon...

A couple of further questions:

- what does one use to cut holes in the tank for the tank connectors etc. Yeah, I know, a 'Tank Cutter'. I have a 'step' drill bit which goes up to 30mm or so, would that do?

- I have read that one should put gate valves in the outlets (cold water taps and DHW). is this recommended by the team?

Thanks again jon N

[jkn]

Yeah, I was looking at that sort of thing, thanks. So the diameters on that set would be suitable?

Fair enough. It is possible they are already fitted, it's one of the next things I have to check before going ahead with getting the bits.

Cheers Jon N

[Dave Plowman (News)]

You need to find out the exact sizes. Old pipework may be imperial, and may need adaptors to metric tube.

22mm (the old 3/4") is the common size for the outlets. The cold water feed usually 15mm.

[GB]

The only way I know to establish the size is to cut the pipe and see whether a metric fitting fits. :)

It's hardly a big expense to get a few 3/4" olives on the off-chance they'll be needed.