Unable to drain water tank

[Mercurial85]

I have tried to search for the answer to this specific question but without success.

We have an external oil boiler and seperate water tank with expansion tank.

I have water dripping through the tundish - as have a few others on the estate - and the most common fix seems to be the recharging of the expansion tank.

However, when I come to train the water tank, I cannot.

If I turn the main water off to the house, there is no hot or cold water which drains from the gaps.

I have tried leaving the main supply to the house on and just turning off the valve which fills the hot water tank and get the same result.

I can therefore never drain the hot water tank because it will only flow out of the taps (and even the little drainage valve which comes off the main tank?) when there is water flowing into the tank.

I presume it’s a pressure issue. The nipple on the expansion tank to recharge is situated too close to the ceiling so I have had to cut a hole into the left to get a valve on the end. If, when I have been messing about, I have released too much pressure from the expansion tank, would or could that be the issue?

Any ideas how I can fix this issue?

 

[SimonG]

An unvented cylinder needs the services of a g3 competent plumber/heating engineer.

 

[Ed the best of the best]

If it’s unvented cylinder, and it’s upstairs , you going to need a G3 plumber, basically what’s he’s going to do it’s isolate the water supply to your heating tank , and drain it trough a drain valve slightly by opening the temperature relief valve or pressure relief valve , after that , when he drained about 20-30 litres of water , he will undo the compression nut on top of your tank to see if there’s any water coming out , if not he will remove the pipe alignment and will create a air vacuum which protects your cylinder from implosion. Don’t do it on your own get a G3 qualified plumber for unvented systems, it involves checking all the safety valves and condition of your expansion vessel and recharge it referring to manufacture instructions . Good luck , I give you my best advice as G3 engineer, it was not everything in detail only basic stuff.