Roca toilet shank sizing help !!!

[DI-OhMy]

Hi,
The fill valve on my old Roca toilet is failing intermittently, sometimes shutting off and other times just constantly running. It seemed like a simple job after researching YouTube so I decided to replace it. Down to Screwfix to buy a Fluidmaster 1/2" Brass shank. Removing old one was a doddle, but then the 1/2" shank didn't fit in the cistern hole. Rather than trying to get a refund I went back and purchased a Viva Universal with 3/8" and 1/2" interchangeable shank options. So 3/8" this is much smaller, seemingly a lot smaller than the original. This turns out to be true as the inlet nut on the mains is to big for the shank, but it does screw nicely on to the new 1/2" shanks, and the original fill valve!!

What are my options here? I have even ordered some drill bits to widen the hole slightly but I don't think should be doing this.

Has anybody had this before? Any suggestions would surely be welcome.

 

[jj4091]

Flomasta Bush 1/2" x 3/8" - Screwfix

Order online at Screwfix.com. Male/female BSP brass bush. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

 

[opps]

I am not a plumber... It might simply be the case that you only need a rubber washer.

Hopefully a proper plumber will be along soon.

 

[DI-OhMy]

Thanks both for your suggestions!

But I feel the 1/2" fill valve shanks should fit through the hole in the cistern and connect to the mains, as the old one did.

The 1/2" & 3/8" measurements, where do they come from? Nothing I measure is bang on that, but I Have no clue what I'm doing. Not a plumber either as you've probably guessed.

 

[Nige F]

They come from BSP threads British Standard Pipe

 

[opps]

I mention the rubber washer because my concealed cistern started leaking in to the pan. I simply had to replace the washer.

Granted, that was a push down cistern, but it was the case that water was leaking under the seal.

I am not a plumber though.

 

[DI-OhMy]

Thanks all.

I used the 12mm diamond drill bit to widen the cistern hole. The original fill valve being plastic was snug but had give. The brass had no give and I didn't want to damges the threads pushing it through.

So all good and no leaks. Not bad for a first time.