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Sealing off isolation valve

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Erico19

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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.
 

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Rubber or fibre

No not steel

No doesn’t need any paste ptfe or anything
 
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The mating metal surfaces that compress the fibre washer need to be clean and smooth and damage free.
Surprised it didn't seal! Did you do up the nut tightly (but not so tight as to damage the plastic thread)?
 
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Prob a bit loose it’s hard to guage with plastic threads best would be to tighten up then turn the water on and tighten slowly until no water is leaking
 
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Basher said:
The mating metal surfaces that compress the fibre washer need to be clean and smooth and damage free.
Surprised it didn't seal! Did you do up the nut tightly (but not so tight as to damage the plastic thread)?
Click to expand...
Thanks for your reply. I just put the washer without any cleaning...I upped the nut nicely and smoothly to align with the plastic threads.
I wonder if I have to put a bigger washer to fit inside the nut instead of putting a 1/2" washer at the top of the inner circle of the isolation valve? Should I use a jointing compound along with a PTFE tape?
Cheers
 
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I looked at it again this morning, using PTFE tape and Jointing compound, I kept one Fibre washer as there was not much space for two....Thankfully, the water did not leak out from the joint when I tested it. Many thanks to all of you for your help :)
 
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Erico19 said:
I looked at it again this morning, using PTFE tape and Jointing compound, I kept one Fibre washer as there was not much space for two....Thankfully, the water did not leak out from the joint when I tested it. Many thanks to all of you for your help :)
Click to expand...
Me again...sorry.
If the isolation valve leak is fixed, I am getting now a leak from the plastric nut at the bottom of the fill valve...I checked the nut; it is tightly adjusted. May be it got a bit misaligned as I kept removing and putting back the toilet cistern...any advice please? Thank you
 
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The nut against the cistern ?
 
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Need to remove it all to find out why it’s leaking might be not centred etc
 
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ShaunCorbs said:
Need to remove it all to find out why it’s leaking might be not centred etc
Click to expand...
I did not screw the cistern on the wall or on the toilet seat when letting the water through; doubt this could be a cause. Here is the picture of the inside, an O-rubber seems at the bottom of the valve. The nut seems too tightly adjusted.
 

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Erico19 said:
outside and at the bottom of the cistern,see please the top arrow in the attached image, leading to the external isolation valve
Click to expand...

Erico19 said:
outside and at the bottom of the cistern,see please the top arrow in the attached image, leading to the external isolation valve
Click to expand...
still water leaking from the nut, see attached image. Could PTFE tape and/or jointing compound added onto the the threads stop the leak?
 

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You can use a small amount of silicon I’m guessing you’ve re used the old washer that seals to the cistern?
 
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Thank you, ShaunCorbs, for your response. Yes, I have kept the same washer on the bottom side of the cistern and at the top of the valve.

I conclude that neither PTFE tape nor jointing compound will fix it. Instead, I will need to add silicone at the edge of the washer.
 
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Erico19 said:
Thank you, ShaunCorbs, for your response. Yes, I have kept the same washer on the bottom side of the cistern and at the top of the valve.

I conclude that neither PTFE tape nor jointing compound will fix it. Instead, I will need to add silicone at the edge of the washer.
Click to expand...

Not at the edge about half way in on the washer etc
 
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ShaunCorbs said:
Not at the edge about half way in on the washer etc
Click to expand...
Thank you very much. Tightening the washer while adding silicone on it stopped the leak. Apparently, I had overtightened the washer, which caused the float ball to shift to the side of the cistern. When the cistern fills up, the internal water flow doesn’t stop completely (water drops) because the friction between the float ball and the inner wall of the cistern prevents it from moving up freely. My toilet system is similar to this one: Replacing a Toilet Tank Float Valve. - https://www.instructables.com/Replacing-a-Toilet-Tank-Float-Valve/. I’m wondering if there’s a quick fix without having to redo the work, now that the silicone has been applied, especially since there’s barely enough space to reach the washer. Thank you."
 
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Erico19 said:
Thank you very much. Tightening the washer while adding silicone on it stopped the leak. Apparently, I had overtightened the washer, which caused the float ball to shift to the side of the cistern. When the cistern fills up, the internal water flow doesn’t stop completely (water drops) because the friction between the float ball and the inner wall of the cistern prevents it from moving up freely. My toilet system is similar to this one: Replacing a Toilet Tank Float Valve. - https://www.instructables.com/Replacing-a-Toilet-Tank-Float-Valve/. I’m wondering if there’s a quick fix without having to redo the work, now that the silicone has been applied, especially since there’s barely enough space to reach the washer. Thank you."
Click to expand...
Sorry, it's me again :)

I opened the isolation valve under the cistern yesterday morning. The toilet wasn't used, but I flushed it twice—much less than in previous days.

This morning, I was horrified to find a leak from the ceiling in the room below. I checked the upstairs toilet, and everything was dry. Purposely, I left the cistern half full last week and there was no leak. It did rain, however, for most of the day yesterday and overnight. I checked the attic, and everything seems dry. The fixed toilet is on the brick side of the house, so I'm struggling to identify the cause of the heavy ceiling leak this morning. Any tips would be greatly appreciated. The boiler was serviced this week by the same company.

I've closed the isolation valve under the cistern since the morning. If it were an internal pipe leak, the leak wouldn’t stop.

Coincidentally, the ceiling leak occurred when it rained heavily yesterday and when I had the isolation valve open all day. Please note that I checked during the day, and the water feed into the cistern stopped.

The leak in the downstairs room was clean water. It occurred at the outer corner of the toilet drain-waste vent system compartment running to the ground.

Thank you.
 
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