Solvent weld Strap on boss with 40mm pipe adapter - how to fit?

[Pile-o-stone]

This is a bit of a weird one as it should be straightforward but isn't (at least for me!)

I have a soil pipe with a strap on boss adapter. I have installed a 40mm boss adaptor inside the boss. It was a snug fit and is rock solid now the solvent has set.

However, the 40mm boss connector is actually 43mm in diameter so the 40mm pipe rattles around inside it and I can't see how it will form a waterproof seal?




Is there a part missing as I was expecting the 40mm waste pipe to be as tight a fit inside the 40mm boss adaptor as the adaptor itself was inside the strap on boss??

[Countrypaul]

40mm solvent weld waste pipe is not he same diameter as 40mm push fit waste pipe! I can't remember which is which.

The solvent weld waste pipe should be a loosish fit into th editting to allow space for the "glue", so don't expect it to be as tight as a push fit fitting.
Have a read of: https://www.diydoctor.org.uk/projects/pushfitfittings.htm

Looks like push fit is 41mm and Solvent weld is 43mm

[Pile-o-stone]

Thanks for the info! I did a bit of googling and it seems that the pipe I have is pushfit. I’ll buy a length of solvent fit pipe and hope it will fit into the push fit elbow socket on the other end. If not, then I have found a universal compression socket that I could use.

Who knew plumbing could be so difficult 😊

[marshman]

Countrypaul is correct. Solvent weld and pushfit are different diameters.  But also Strap bosses are different as well. Some will take a solid insert as they are designed to cope with 50, 40 & 32mm.  Others have a rubber insert such as this:

https://www.screwfix.com/p/floplast-boss-adaptor-40mm-5-pack/89174

I find it is always best to make sure all components are from the same manufacturers to ensure they fit correctly.

From the sound of it you need a push fit to solvent weld adaptor:

https://mcalpineplumbing.com/plastic-chrome-fittings/multifit-waste-fittings/s18-absc-straight-connector-pushfit-x-solven-weld

then a short bit of 40mm solvent waste to fit into the soil pipe.

One other thing to note. As far as I know push fit stuff should not really be used outside as it is not UV stable. After a few years the plastic becomes very brittle. Solvent weld all the way for me, fit and forget, just remeber to fit access eyes to be able to clean it out when it inevitably gets gunged upo in a few years time.

[Countrypaul]

Unfortunately, its all due to metrication as far as I can see 

Try looking at 50mm downpipe for gutters and getting an adapter for that so that you can use a gulley(?) without a grid, easy for 68mm, but seems no chance for "50mm" which, incidently, is differernt size to 50mm waste pipe (its more like 45mm). Only solution I have found so far is rubber cap that can handle various smallish pipe sizes.

[Pile-o-stone]

Thanks marshman (and countrypaul) for yopur replies. Originally the boss had a rubber insert but it was leaking a bit. I replaced with a solvent weld insert but didn't realise that the waste pipe has to be replaced too. Interestingly, if the strap boss are different as well, then perhaps that explains why the original rubber insert wasn't working? The solvent weld insert fitted perfectly, so maybe the boss strap was a solvent weld and the original owner of the house had used a pushfit rather than a solvent weld insert.

I'll report back how I get on once I can get down to the DIY shop and buy some solvent weld pipe. Thanks for your prompt help so far!

[Pile-o-stone]

A quick trip to the DIY store and I’ve now attached the 43mm solvent weld pipe snugly into the boss and there are no more leaks. Thanks again for your help

[gravyminer]

yeah plumbing can be a tease and while obviously I dont recommend any of those amazing modern mastic products for mismatched waste fittings .........

I do have a solution for joining odd size pipes together -

https://www.flexseal.co.uk/products/flexible-couplings/adaptor-couplings/

a range of 35-420mm diameter covers most low pressure / gravity plumbing challenges

[knighty]

yeah plumbing can be a tease and while obviously I dont recommend any of those amazing modern mastic products for mismatched waste fittings .........
I do have a solution for joining odd size pipes together -
https://www.flexseal.co.uk/products/flexible-couplings/adaptor-couplings/
a range of 35-420mm diameter covers most low pressure / gravity plumbing challenges

I don't like those much

I'd maybe use one if I was going from smaller to larger, on a downward slope, and could push the smaller pipe up inside the larger one

but other than that I think there's too much scope for stuff/dirt/junk to get snagged up inisde the pipe



saw one used in the reverse of that  just said... larger pipe to smaller pipe... was destine to fail