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Discuss Basin waste size help in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

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Hello.

I am in the process of trying to replace the Unslotted basin waste on the hand basins in my bathroom, but am a little confused with the sizing as I have little experience of plumbing. From what I can see the the waste I have removed has a diameter of 40mm but the trap that this screws into has a waste pipe inside of it with a 32mm. I’m hoping to just replace the waste and leave the rest as is.
I know most hand basins take a 32mm waste but this doesn’t seem to fit with the size of the one I have removed but does with the trap pipe. Pictures attached.

my question is do I need to buy a 32mm or 40mm waste?
32F6A2AE-9437-4744-8BDF-CE19CFF38B6C.jpeg
F6E9E6F6-378E-44FA-B2EC-99E43CEB6B67.jpeg
 
If the outlet size of your trap to wastepipe is 32mm (1 & 1/4” standard) then purchase a 1 & 1/4” unslotted basin waste.
 
If the outlet size of your trap to wastepipe is 32mm (1 & 1/4” standard) then purchase a 1 & 1/4” unslotted basin waste.
Agree. The 1.25" is the nominal inside diameter of the tube (1.25" BSP thread).

More simply, however, you need to fit the basin waste that is correct for your basin: almost certainly a 1.25". If (very unlikely) that is wrong for the pipework, then you'll need to deal with that as a separate issue.

OP I hope you're aware that an unslotted basin waste is unusual? However, if that is what you need, then go ahead.
 
Thanks all.
There is no overflow on the basin and the waste I removed was unslotted so I’m assuming unslotted!
thanks for your help.
 
yes unslotted then grab some plumbers mate while your at it to install the waste
 
I'm not reacting to this, though you know I want to...
Not to worry Ric, bit late but I'll react to it.
Well done Sean thank god you suggested plumbers mate - the correct solution to seal waste to basin.
I'm so pleased you didn't suggest silly-con-carny or some other hateful jollop which would permanently weld the waste to the basin preventing maintenance, cleaning, care, unblocking and replacement in future.
Good on you.
 
Not to worry Ric, bit late but I'll react to it.
Well done Sean thank god you suggested plumbers mate - the correct solution to seal waste to basin.
I'm so pleased you didn't suggest silly-con-carny or some other hateful jollop which would permanently weld the waste to the basin preventing maintenance, cleaning, care, unblocking and replacement in future.
Good on you.
Okay okay: now you got me in! I hate "Plumber's Mait".

Or better: I hate "Plumber's Mait"!

It's supposed to be able to be used for sealing sockets in spigot and socket type rainwater systems such as cast iron and it softens and falls into the downpipe. Fail!

It's supposed to be used for sealing wastes in. It develops a gloopy stuff that runs under the basin with use (hot water presumably) and is sticky and bleurgh (I had a cleaning job once and made it my mission to remove this - it took some time). Fail!

It is non setting. While this can be a good thing (reseals the basin waste after disturbance), it is also a source of minor weeps I have come across in various locations (installation by others). If you use silicone, the silicone sticks the waste in place and disturbance is unlikely. Often not bad enough for the layman to notice, but very often you will see a bit of limescale under/around a basin waste for this reason. Fail!

Plus, was taught in college that "Mait" shouldn't be used in conjunction with anything plastic/grp, so not suited to most bath tubs. Not sure if this is true, however, as I don't know that "Mait" genuinely leaches oils that may harm such substances.

Advantage is that it is removeable? How often do you need to remove and re-use a waste? I've done it, but rarely. I had used "Plumber's Gold" 'hybrid polimer technology' silicone-like substance to seal a waste into a bidet and the bidet was faulty. It took me less than 10 minutes to clean up the waste sufficiently to remove the waste and I refitted to the new bidet without issues. Perhaps the problem is that some people like to use a whole tube of the stuff?

I've yet to be convinced that "Plumber's Mait" has a place in my van. To be honest, I'd be more open to the idea of using an old-fashioned linseed oil putty. At least this would set and hold things firm. In fact, I know an old plumber who swears by "Plumber's Mait" but then admits that he doesn't actually mean the product that is branded "Plumber's Mait" but linseed oil putty...

If removeability is an issue, I wonder what people think about basin mates? The type with a conical rubber seal that mean you don't need to use any sealant whatsoever. I once used one in a situation in which I definitely did not want to disturb anything (a 1.25" kitchen waste with brass banjo overflow that was just waiting to start leaking the moment it was touched) and was so impressed that I bought two more just to have them in case I needed them: I felt they were excellent problem solvers. They feel a bit DIYey, but they work so well - unless there are known issues with durability? I generally don't use them, however, due to cost.

"Plumber's Mait" eurgh....

[endeth the rant]
 
Last edited:
If you want to use the 40mm unslotted waste with a 32mm trap. The simplest way to do this is use a mcalpine thread reducer. About £1.80 so a cheaper solution than buying a new unslotted waste.
 

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