Distorted and crumpled HW tank.

[kentishman]

I noticed today that my Hot Water tank has become distorted and a bit crumpled, as these photos show. The only reason I can think of is that about a year ago we replaced the downstairs cloakroom basin and to save draining the HW tank, we shut off the feed from the cold water tank to the HW tank and placed a bung in the vent pipe that goes from the HW tank to the cold water tank. I presume it's been like this for a while and I haven't noticed as normally the tank is covered with a loose-fitting insulation jacket. Could atmospheric pressure have caused this distortion when we opened the taps with the bung in place and with the feed shut off? And should I be concerned, do I need to replace the HW tank?

 

[seco services]

i would change it.

when working on the hot water side you don't need to bung the vent just isolate the cylinder gate valve from the cws tank and open a tap that will drain the top level on the cylinder and stop the hot flow so you can work on it.

 

[kentishman]

Thanks for the quick reply, and for the good advice.... It's obvious really I guess!!

I don't suppose anyone knows how much a crumpled tank would fetch as scrap nowdays?

 

[seco services]

i run mine in for about £25 - £30 depending on the prices.

 

[blondini]

The bung was a bad move and dangerous.
Water is incompressible but it expands when heated and contracts when cooled. I'm guessing that the water in the tank was cooling whilst the bung was in place. Atmospheric pressure did the rest. If it had been heating up it could have burst the tank if the bung held.

If it's been ok for a year though, I wouldn't worry but I'm not a pro.

 

[seco services]

If it's been ok for a year though, I wouldn't worry but I'm not a pro.

you will when 117 litres comes through your lounge ceiling.

 

[kentishman]

The bung was a bad move and dangerous.
Water is incompressible but it expands when heated and contracts when cooled. I'm guessing that the water in the tank was cooling whilst the bung was in place. Atmospheric pressure did the rest. If it had been heating up it could have burst the tank if the bung held.

With hindsight I agree the bung was a bad move, but I'm not sure it was dangerous as the bung was one of those push-fit rubber things that would have easily popped out if the pressure was positive within the pipework/tank. Besides, the pipework I was working on was open and the water would have expanded in my direction!

 

[seco services]

boiler wasn't heating the tank at time not a prob.

 

[Bahco]

DO NOT USE!

If the copper has been weakened (especially at the joints) it can burst and cause a lot of damage.

Decommision it so it can't be used.

 

[EliteHeat]

you will when 117 litres comes through your lounge ceiling.

 

[doitall]

you will when 117 litres comes through your lounge ceiling.

Actually it will be double that with the water in the storage tank following it

 

[seco services]

ya but that follows after the hot water to cool ya down

 

[kirkgas]

given the state of the cylinder i would drain it down before i went to bed i couldn't sleep with that in my house it could split and flood anytime,depending on the temp of the stored water it could scald someone, there was a case recently where a baby died from scalding when a cylinder in a loft burst right above the cot and gallons of water poured on top, ( in this case the stat was faulty and the water temp was very high) but even stored water at 60degrees will cause massive damage, drain down now!!

 

[scatmanjohn]

With hindsight I agree the bung was a bad move,

What was the bung going to achieve anyway

Apart from killing the cylinder i mean.

 

[Onetap]

Could atmospheric pressure have caused this distortion when we opened the taps with the bung in place and with the feed shut off? And should I be concerned, do I need to replace the HW tank?

Yes. Draining the cylinder caused a partial vacuum in the cylinder and no air could get in to relieve the vacuum. The atmospheric pressure partially crushed the cylinder. A better vacuum would crush it almost flat. 14.7 psi, surface area of cylinder is, oooh, rather a lot of square inches, you can do the maths.

It may hold, it may not. Your gamble.

2nd picture, no it's not what I'd thought, it's an Essex flange. Why is the washer/gasket split?

You're lucky it didn't provide an indoor water feature before it got squashed.