Low level toilet cistern leak!

Niv

My low level toilet cistern leaked this morning. It looks like its just the siphon connecting to the pipe that leads to the pan. Looking at the gasket it looks like it is slightly depressed but not convinced that it failed, thinking that the screw has worked loose from repeated leaning on the cistern over years. 

My questions;
- Should I just replace this gasket, just in case? 
- can/should I use plumbers mait on the gasket to improve the seal? Or is that unnecessary ?
- Should there be a seal on the underside of the cistern? There isn't one and looking at repalcement units they do not seem to have them so assume not - but while I am here I just want to cover all bases! 

Cheers!

Niv

Also - if I should replace this - what is it called, when I search it mainly see closed coupled doughnut type washers.

found a 2" one in screwfix but mine is 3" 
Looks like this but needs to be 3"
https://www.screwfix.com/p/fluidmaster-cistern-coupling-washer-2-/884JM?gclsrc=aw.ds&gad_source=1&gbraid=0AAAAAD8IdPxbMSbDlAr7psFQeDcPQIoIf&gclid=Cj0KCQjwhr6_BhD4ARIsAH1YdjDuEGHc4k9FlJb9FH9xzBemgz0G3sz19EAf_nL3OroddZhLob2ytIAaAmVqEALw_wcB&gclsrc=aw.ds#product_additional_details_container

stuart45

Have you tried tightening up the nut a bit?

Niv

stuart45 said:

Have you tried tightening up the nut a bit?

I had a go, but will try again.

stuart45

If it doesn't work stick a new washer in. There shouldn't be a washer underneath the cistern.

Niv

stuart45 said:

If it doesn't work stick a new washer in. There shouldn't be a washer underneath the cistern.

I didn't think there should be but wanted to check. I have tightened it up and its ok at the moment, but my thought on the plmmers mait was wondering if it would help the seal and not be a 'bodge' (as I already have some and cant find a replacement washer ).

If it still leaks I will end up buying a whole new unit, I found something in toolstation for under a tenner so at least I can get it done today.

FreeBear

Fitted a new low level cistern & pan a little while back. There is a rubber sealing washer under the siphon inside the cistern (and another under the fill valve). Also have a thin(ish) plastic washer on the outside. When fitting, I put a thin smear of silicone sealant on both washers before assembling.

stuart45

Plumber's mait will probably work. Normally the washer just gets replaced, as you have to get the washer out anyway, so it's just as easy to stick a new one in.
One of the plumbing merchants like City plumbing should have a replacement.

stuart45

What size is your flush pipe(diameter)?

Niv

stuart45 said:

What size is your flush pipe(diameter)?

cant check at the moment but I have one of these:

https://www.toolstation.com/viva-skylo-dual-flush-syphon/p51299

It fits the pipe snugly so believe that is the correct size - It has been in place approx eight years since I installed it, so I don't think its anything other than working lose / seal perishing.

I have cleaned /dried the area, re-seated it and tightened it by hand as far as I could and so far have had no reports of further leaking so fingers crossed it was just that it worked loose. 

stuart45

That's a standard 1.5 inch flush pipe, so should easily get a replacement washer if ever needed. Looks like it just needed tightening up as you did. I've done mine a couple of times.