Sealing off isolation valve

[Erico19]

Hi,
The isolation valve feeding my toilet cistern was leaking. After considerable effort, I was able to lift up the cistern to put an O-ring washer around the top of the inner circle referred to with an arrow in the attached image. Unfortunately, when I let the water through, there was a burst leak. Should I use a flat-ring washer instead? If so how can I get the right size?Should I put the ring at the top or push it down?
A friend suggested using also a jointing compound along with a PTFE tape; If a washer is enough, I won't buy these products

Thank you.

 

[Chuck]

Wrap several layers of toilet tissues around the suspect valve/joint and hold in place by tying with a piece of elastic, e.g. cut open an elastic band. This will allow you to rule the isolator and nearby joints in or out.

What direction does the outside wall face and what direction was the rain coming from? Can you post a couple of pictures of the outside wall?

BTW, I haven't got the time right now to read two dozen posts to figure out exactly how you fixed the leak between the inlet valve spigot and the isolator but I suspect you bodged it. The way I would have dealt with it would have been a new float valve with a brass spigot and, since it is corroded, a new isolator. The seal should be made by a fibre washer, no silicone needed.

 

[Erico19]

Wrap several layers of toilet tissues around the suspect valve/joint and hold in place by tying with a piece of elastic, e.g. cut open an elastic band. This will allow you to rule the isolator and nearby joints in or out.

What direction does the outside wall face and what direction was the rain coming from? Can you post a couple of pictures of the outside wall?

BTW, I haven't got the time right now to read two dozen posts to figure out exactly how you fixed the leak between the inlet valve spigot and the isolator but I suspect you bodged it. The way I would have dealt with it would have been a new float valve with a brass spigot and, since it is corroded, a new isolator. The seal should be made by a fibre washer, no silicone needed.

Thank you for the tip. The joint pipe which outs the water from the tank was loosely connected.