Hi all,

 

I have been landscaping my drive and found that a long section of water main was metal pipe which was very corroded and brittle. I decided that while I was digging it all up and would replace with 25mm MDPE. The main supply stop cock is near the boundary, it is a metal stop tap with a metal female BSP socket on the domestic side. I purchased a male BSP to 25mm MDPE plastic coupling which fits fine but keeps weeping. I think the weep is at the MDPE male to metal female joint rather than the 25mm MDPE pipe/fitting joint. I did apply some PTFE and I made it tight but stopped going too hard as was worried that the plastic male would crack or deform if overtightened into a metal female socket. I wonder if I should try to pinch it a bit tighter or should I try a thicker wrap of PTFE? thanks.

 

the fitting is one of these: 

 

 

 

No tape on the MDPE end, the threads do nothing for sealing, you probably pushed the o ring into the fitting.

just re read and it’s the threaded end into fitting.  sorry my mistake

Edited June 28, 20233 yr by markc

thanks, yeah it's the male threaded end rather than the 25mm MDPE pipe into the o-ring fitting. I've had leaks on those as well, but seem to be if the pipe is scratched and the o-ring doesnt make a clean seal.

Make sure the pipe is going in to the fitting dead straight, with no side tension. It'll likely leak. Came across 100s of cases like that in new site when we were surveying new meter box installs. If it's the bsp thread that's leaking, try putting the original fitting back on and use a compression adapter on the stub of original pipe.

 

If it's leaking at the stoptap side, you could call the water company and ask for a replacement.

Edited June 28, 20233 yr by Conor

unfortunately the old fitting went the way of the skip and is long gone, I only noticed the weep some time later. I think I can only try to sure up the BSP thread join with more PTFE and braver extra 1/4 turn. I might buy another fitting first in case it all goes wrong and I overtighten it. 

 

I noticed MDPE fittings are a bit leak prone, as you say, if the pipe isnt dead straight into the fitting and I've had them leak with scored pipe where the o-ring cant make a perfect seal. I wonder if many homes have small leaks between meter and the house for these reasons and just arent aware of it

 

A brass BSP>mdpe adapter perhaps? With some loctite 55 wound hard into the existing BSP fitting?

 

Plastic BSP fittings will creep if wound tight anyhow.

make sure you have the plastic insert inside the MDPE pipe before tighting.

Brass inserts for brass fittings on mdpe?