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Basic query about plastic waste pipes...


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I will shortly be entering the foray of changing waste pipe plumbing.

 

Having measured what we currently have it is about 41mm outside diameter, and using push fit fittings with no solvent weld.

All pipe sold in our local Wickes (white or black) appears to be sold as 40mm, but actually measures about 43mm externally.
 

Clearly 43mm external diameter pipe will not allow me to re-use push fit fittings that currently are a tight fit with pipe that is about 2mm less in diameter.

A bit of Googling suggests both pipe sizes are confusingly sold as 40mm, but that the 41mm is intended for push fit, whereas the 43mm is intended for solvent weld.

Can anybody please confirm that is the correct information?

 

If so it seems I can't actually order 40mm pipe, (or 41mm pipe), but instead need to actually go somewhere to measure it before purchase to be sure.  Right or wrong? 

 

Alternatively if I make sure it is specified as 40mm push fit, can I be sure it will actually fit in 41mm fittings?

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We used to sell this stuff in the independent merchants I used to manage. Sadly, plastic plumbing is an absolute nightmare, each manufacturer has its own  view of what is the right size. Nominally, in everyday use, there are 2 waste pipe sizes, 40mm & 32mm. To add further  aggravation the size of solvent weld or push fit for each manufacturer is a different size so you cant mix and match those. The push fit & solvent weld are also different types of plastic so you cant use push fit pipe in solvent weld fittings.

The only way to be sure of a proper job is to use the same manufacturer throughout your particular job. You can get round most difficulties in mixing fittings by using the compression versions, they will accommodate the differences in manufacturers. 

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13 minutes ago, sharpness said:

We used to sell this stuff in the independent merchants I used to manage. Sadly, plastic plumbing is an absolute nightmare, each manufacturer has its own  view of what is the right size. Nominally, in everyday use, there are 2 waste pipe sizes, 40mm & 32mm. To add further  aggravation the size of solvent weld or push fit for each manufacturer is a different size so you cant mix and match those. The push fit & solvent weld are also different types of plastic so you cant use push fit pipe in solvent weld fittings.

The only way to be sure of a proper job is to use the same manufacturer throughout your particular job. You can get round most difficulties in mixing fittings by using the compression versions, they will accommodate the differences in manufacturers. 

exactly.

 

if you go to Wickes or similar it shouldn't be too difficult to pick compatible pipes and fittings - just read the labels very carefully and ask for advice if unsure.

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Toolstation and Screwfix do both solvent weld and push-fit/compression pipes and fittings. The two types are not compatible with each other except that solvent weld pipe will squeeze into compression fittings, but normally only by dismantling the fitting first. 

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I was once advised by a marine surveyor to only use compression fittings on plastic waste pies on our boat, as they are the only type which will nopt come apart in use  but can be dismantled if needed.. To be honest Alan, plastic waste pipes and fittinge are so cheap, it may be easier in the long run to replace the whole lot with new ones, which is what I ended up doing.

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3 hours ago, alan_fincher said:

I will shortly be entering the foray of changing waste pipe plumbing.

 

Having measured what we currently have it is about 41mm outside diameter, and using push fit fittings with no solvent weld.

All pipe sold in our local Wickes (white or black) appears to be sold as 40mm, but actually measures about 43mm externally.
 

Clearly 43mm external diameter pipe will not allow me to re-use push fit fittings that currently are a tight fit with pipe that is about 2mm less in diameter.

A bit of Googling suggests both pipe sizes are confusingly sold as 40mm, but that the 41mm is intended for push fit, whereas the 43mm is intended for solvent weld.

Can anybody please confirm that is the correct information?

 

If so it seems I can't actually order 40mm pipe, (or 41mm pipe), but instead need to actually go somewhere to measure it before purchase to be sure.  Right or wrong? 

 

Alternatively if I make sure it is specified as 40mm push fit, can I be sure it will actually fit in 41mm fittings?

 

Yes. 

 

I mean no. 

 

Solvent weld waste pipe brands are generally universal and an accurate  fit with each other, but not push fit. 

 

I doubt that helps.....

 

 

 

Edited by Mike the Boilerman
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8 hours ago, Mike the Boilerman said:

 

Yes. 

 

I mean no. 

 

Solvent weld waste pipe brands are generally universal and an accurate  fit with each other, but not push fit. 

 

I doubt that helps.....

Having recently plumbed in a replacement 1 1/2 bowl sink I can attest to the fact that...

 

Not all push-fit pipes and fittings fit each other. And...

 

The ‘compact’ waste kit sold by Screwfix is incorrectly named. 
 

That probably doesn’t help either. 

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10 minutes ago, WotEver said:

Having recently plumbed in a replacement 1 1/2 bowl sink I can attest to the fact that...

 

Not all push-fit pipes and fittings fit each other. And...

 

The ‘compact’ waste kit sold by Screwfix is incorrectly named. 
 

That probably doesn’t help either. 

 

And to add to the knowledge base, I can confirm the term 'push-fit' only tells you the half of it.

 

The complete term is 'push-fit, spontaneously self-un-fit'.

 

I learned early in my plumby career never to use push-fit waste systems. 

 

 

 

  

I think the effect is something to do with the massive huge coefficient of thermal expansion that placky pipe possesses. 

 

 

 

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1 minute ago, Mike the Boilerman said:

 

And to add to the knowledge base, I can confirm the term 'push-fit' only tells you the half of it.

 

The complete term is 'push-fit, spontaneously self-un-fit'.

 

I learned early in my plumby career never to use push-fit waste systems.

  

 

There appears to be very little prospect that what is currently fitted would ever come apart in normal use.

 

We have had the boat well over 4 years, and based on experience to date, I'd be very happy to use the same again.

 

Elsewhere on the boat though, solvent weld that had been used as the overflow on the cold water tank was found to be leaking.

 

Previous work by others on Flamingo often defies what you might expect!

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2 hours ago, WotEver said:

 

The ‘compact’ waste kit sold by Screwfix is incorrectly named. 

I guess you might mean this one which isn't very compact at all:

https://www.screwfix.com/p/mcalpine-space-saving-sink-appliance-p-trap-white-40mm/66149?_requestid=254562

 

I do like these ones from Toolstation though but the reviews are hardly glowing:

https://www.toolstation.com/espace-extra-flat-sink-trap-1-12/p54424#reviewTab

 

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