New Cistern donut Seal - Question

[RK_London]

Old Villeroy and Boch cistern had leaky donut seal ( see pictures below). Replaced donut seal with 2inch seal from Villeroy and Boch.

Noticed the seal rested on the outer lip of the toilet bowl ( second picture) so the cistern was slight raised by a few mms. Didn't think this was an issue once cistern fixing bolts were tighten. After tightening bolts, there was still a few mm gap between the cistern and the toilet where the fixing bolts are attached. But bolts were tight and seal looked ok.

Had an issue. The toilet worked ok until I tested the overflow pipe. Filled tank to the very top and the seal began to fail and was leaking. When I lowered the height of the overflow, the seal was ok. Looks like the extra weight if water is messing up the seal.

Not sure what I have done wrong.

Any ideas anyone?

 

[footprints]

Looks from the seal that it is clamping down more on one side than the other, is the cistern clamping down level, cannot see the wall fixing. Is that or the pipe pulling it off line perhaps?
Is the seal identical to the one you removed?

Lots of options
https://www.toiletspares.co.uk/search/for/doughnut/

 

[Madrab]

Yep +1, you can see from the mark on the new seal that the cistern isn't sitting straight on the pan and it's getting pulled more one way than the other so the seal isn't sitting central. Did you dry test fit the seal on the table of the pan first to see how it would (edit) sit?

 

[RK_London]

Thank you Madrab and Footprints for helpful replies.

Looks from the seal that it is clamping down more on one side than the other, is the cistern clamping down level, cannot see the wall fixing. Is that or the pipe pulling it off line perhaps?
Is the seal identical to the one you removed?

Lots of options
https://www.toiletspares.co.uk/search/for/doughnut/

I replaced the old seal (first picture) with a foam seal from Villeroy and Boch (Villeroy and Boch Fastening Set for Cisterns) to make sure I was using the correct seal. When I did a dry test fit, looked ok although the cistern sat a few mms higher than before with a small gap between the cistern and pan which I assumed would disappear after tightening the fastening bolts. But the gap didn't disappear. I will try another doughnut seal and see if the cisterns sits better before fastening the bolts.

The previous plumber used silicone to secure the cistern (see picture below). The bolt next to angle valve has a small drip - can I use plumbers mait putty on this?

 

[Madrab]

. But the gap didn't disappear

That's ok if the gap doesn't disappear , in fact that may be better as it means that the seal is stopping it and must definitely be making contact on both sides and creating the seal. Getting it sitting central is key though.

There may be a more exacting seal that allows the cistern to sit flat but that would be one that would fit perfectly over the nut, the one in the pics looks a bit loose, as it would probably need to be 'squeezed' over the plastic nut and will fit tighter into the internal groove.

 

[RK_London]

There may be a more exacting seal that allows the cistern to sit flat but that would be one that would fit perfectly over the nut, the one in the pics looks a bit loose, as it would probably need to be 'squeezed' over the plastic nut and will fit tighter into the internal groove.

You are right - noticed the fitting of the new doughnut seal abit loose around the fill valve nut - was expecting as you say more of a 'squeeze'.

Another separate issue you might be able to help with - any idea why my new fill valve is causing water hammer but the old one isn't? I have had to put old one back on. Is there an adjustment I need to make?

 

[Madrab]

any idea why my new fill valve is causing water hammer but the old one isn't?

You're new valve is closing quicker than the old, causes a shock to travel down the pipework, creating hammer. Is the toilet on the mains? If so did the new valve come with a plastic coiled flow limiter inside the fill tube or maybe separately?

 

[RK_London]

You're new valve is closing quicker than the old, causes a shock to travel down the pipework, creating hammer. Is the toilet on the mains? If so did the new valve come with a plastic coiled flow limiter inside the fill tube or maybe separately?

Toilet is connected to mains. Using a Geberit 380 fill valve - will take a look to see if it has a flow limiter