Hot Water Cylinder max. head

[jgh]

I've just moved my cold water storage tank to the next floor up, to give enough head for a shower to work. In scrabbling around in the airing cupboard I found half a label on the hot water cylinder saying "Grade 4 - ???? maximum 6 metres". Doing some background checks confirms this means "maximum head of 6 metres".

Grr. With the cold water tank now moved, the hot water cylinder has a head of 8 meters. Is there a safety margin on cylinders that this is within, or do I have to rip out the airing cupboard and replace the cylinder? There's no room to move the cylinder upstairs with the cold water tank.

Thanks.

(I should never have started this job....)

-- JGH

[David Hansen]

On Thu, 18 Oct 2007 20:20:24 -0700 someone who may be [e-mail] wrote this:-

Presumably the cylinder is connected up and has not failed yet.

You might get away with it, at least for a time. You will note from

that such a cylinder is pressure tested to 1 bar, which is more than an 8m head.

It may survive in this situation for months or years or decades, who knows? However, if it does fail a lot of hot water may well pour over someone.

I wouldn't leave it as it is.

[Doctor Drivel]

As he now has the expense of installing new cylinder he may want to consider a heat bank (thermal store) cylinder and have mains pressure water throughout the house. No pumps and great showers.

[jgh]

I haven't refilled it yet.

I can picture the rooms filling up to the windows...

I've put a temporary bypass in so I can test the rest of the pipework, and shall just have to live without hot water until next week until I order a number 3 cylinder.

-- JGH

[jgh]

According to

= 10.19716m of water

Eeee. So tempting. 20% margin. I shall have to do some careful measuring and a bit of testing. I've spent a week without hot water :(

-- JGH

[Pete C]

Hi,

A grade 4 cylinder will take a suprising amount of pressure:

See para 2.2.2

I'd be inclined to rig up a hose to give a 10m head on the cylinder and leave it a couple of days to check it doesn't leak (10m head =

1bar).

cheers, Pete.

[jgh]

Carefully measuring shows the bottom of the cylinder to be

7.54m below the top of the header tank, so 25% within the 10m (1bar) test pressure. I shall fill it up, and then turn off the stop-tap to the header tank (so I only have a 25gal flood!) and leave it a few days to test.

-- JGH

[David Hansen]

On Fri, 19 Oct 2007 12:14:22 -0700 someone who may be [e-mail] wrote this:-

It will not sound funny if the water pours over someone and kills or injure them. That may sound far fetched, but it is not as far fetched as many think. The last well known death involved a baby and a pressurised cylinder in the loft, so it is not directly compatible to your situation, but there is still a risk. There is a fair amount of energy stored in a hot water cylinder.

As I said, the cylinder may well last for decades in this condition, but I wouldn't take the risk. I would however use the opportunity to consider installing a cylinder with a solar coil or a thermal store with provision for solar.

[jgh]

In the current location, a bust HWC will gradually fill up my cellar, ruining the computer equipment in the basement at the front, and probably leaking into the neighbours' cellars,

My boiler is on it's last elbows anyway, and I want any replacement to not be in the bathroom as the current one is, so I'm tempted to go for a combi and do away with the cylinder anyway. The only concern I have is I have got used to having 25gal of hot water on instant tap whenever I get into the shower, and I would like at some future point to harvest sunlight to top up the water heat.

-- JGH

[Doctor Drivel]

Use a heat bank (thermal store)

[David Hansen]

On Tue, 23 Oct 2007 03:06:05 -0700 someone who may be [e-mail] wrote this:-

Whether such things are worthwhile partly depends on how much simultaneous demand there is for hot water. They can work reasonably well in single person flats, but generally run out of steam with larger households, where a stored water system is a better option.

I suggest that you have a look around to see where a boiler and cylinder/themal store could go. Remember while looking that a combination boiler is going to be larger than an ordinary boiler, though not as large as an "ordinary" boiler plus cylinder.