Any way to reduce hole on vanity unit for basin waste fitting?

[Joe Fixit]

Hi,

I know, I should have double checked but partner bought the basin bowl she wanted and only realised the hole on our vanity unit is too big for the fitting. The bowl should sit on this silver plate, waste pipe going down the hole and then clamped to secure. Problem is the holes too big and therefore is not secured, as the securing nut cannot be screwed against the underside of the vanity unit.

Is there any product that I can secure to the unit to reduce this hole or any workarounds? Universal bowl fitting?

 

[CountryFan]

Would an additional backnut for the waste work?

 

[Joe Fixit]

Would an additional backnut for the waste work?

Interesting. I guess I would need a back nut which is the same thread size and diameter of the waste pipe but the 'flat section' of the back but would need to be much larger so it can clamp onto the wood

 

[Joe Fixit]

Looking at it, the back nut would need to be massive!!

Took a photo of the current nut

 

[yorksbuilder]

Those parts fix to the basin, not to the unit. The waste then passes through the hole in the unit, and the trap is then attached to the end of the waste threaded section

 

[Scally-Ho]

I wouldn't rely on a fully plastic waste fitting to secure the bowl to the base as the plastic would sheer before everything was tightened to my satisfaction.

 

[Joe Fixit]

Those parts fix to the basin, not to the unit. The waste then passes through the hole in the unit, and the trap is then attached to the end of the waste threaded section

I thought that but the bowl just wobbles? Or is this reliant on silicone adhesive?

 

[Scally-Ho]

Silicone is not an adhesive, only a product for sealing.

 

[Joe Fixit]

I wouldn't rely on a fully plastic waste fitting to secure the bowl to the base as the plastic would sheer before everything was tightened to my satisfaction.

Do you mean the black plastic bit surrounding the hole?

Nothing screws onto or would squeeze it. Only strain is the weight of the bowl?

 

[Joe Fixit]

I'm a bit lost. How does one secure this or are they simply incompatible?

Bowl can't simply sit on the hole with or without the supplied black cap thing.

The hole is just under 8cm in diameter, is this correct?

 

[Scally-Ho]

What do the fitting instructions say about mounting the bowl securely onto base? The manufacturer must have had something in mind when it was produced.

 

[Joe Fixit]

What do the fitting instructions say about mounting the bowl securely onto base? The manufacturer must have had something in mind when it was produced.

Like any other bowl/vessel sink but the howls too big. The back nut should be clamping onto the vanity which I can't.

 

[CountryFan]

Maybe cut a piece of plywood, with a waster hole to sit between the hole and the basin waste backnut?

 

[Scally-Ho]

Then you'll need a flange/washer to both cover the enlarged hole and act as a clamping down flange for the waste fitting assembly to grip upon.

 

[Joe Fixit]

Interesting. Will keep this as last resort

Maybe cut a piece of plywood, with a waster hole to sit between the hole and the basin waste backnut?