Basin waste leaking - do I have the right one?

[boston1832]

I have a cupboard-type vanity unit with washbasin which was fitted about 8 years ago by a local plumbing contractor. The job seemed to be fine until recently when I noticed that the basin waste was leaking slightly into the cupboard below the basin, and examination showed that it was around the nut on the bottom of the basin waste fitting (i.e. as opposed to any of the waste joints further down).

When I removed the waste I found that they had added a thick (around 6-8mm) bead of silicone underneath the washer between the top of the waste and the basin (see photo). There as also a large amount of silicone around the thread at the bottom of the fitting. I’ve not done many of these before but it looks to me as though they had to do this because the underside of the top of the fitting (i.e. the bottom of the flange that sits in the basin) didn’t fit the basin shape and left a large void. I realise this can’t be the cause of the leak on the bottom nut but it doesn’t look right and and I’d like to know if there’s a better way.

Is my assumption correct that the gap just needed filling or have they just bodged a careless install? A few other aspects of their job showed pretty poor attention to detail such as not understanding the vanity unit fittings and installing it off-plumb to the wall.

Do I have the right waste or would a different type fit better? They replaced the basin, vanity unit and waste but kept the same tap unit for some unknown reason, hence me wondering if they’ve just used this waste because it happened to be there.

I’ve refitted it with a bit more silicone and it’s still leaking, so it looks like a Basin Mate might be the next step.

Thanks in advance,

Chris

 

[Madrab]

The top of the basin waste doesn't really matter as far as watertight is concerned - all that seal is created underneath. The top can allow seepage of water past the plug and into the waste so the basin would slowly empty. Clean that top part up and a little more to seal.

The key though is underneath, that all needs to be really dry and clean. Drop the waste in and then fill around the section where the threaded body of the waste exits the throat of the basin waste hole with a bead of silicone, enough to bridge the gap between the threads of the waste and the side of the basin hole. Not too much so it fills and blocks the overflow if there is one then fit the washer(s) and nut. Any silicone squeezed out when tightening then wipe that around the nut and around the threads at the base of the nut to add more of a seal.

Worst case though then a basin mate may do the job.

 

[boston1832]

The top of the basin waste doesn't really matter as far as watertight is concerned - all that seal is created underneath. The top can allow seepage of water past the plug and into the waste so the basin would slowly empty. Clean that top part up and a little more to seal.

The key though is underneath, that all needs to be really dry and clean. Drop the waste in and then fill around the section where the threaded body of the waste exits the throat of the basin waste hole with a bead of silicone, enough to bridge the gap between the threads of the waste and the side of the basin hole. Not too much so it fills and blocks the overflow if there is one then fit the washer(s) and nut. Any silicone squeezed out when tightening then wipe that around the nut and around the threads at the base of the nut to add more of a seal.

Worst case though then a basin mate may do the job.

Many thanks for the quick reply Rob - will give that a go.

Chris