MDPE to HEP20

[turnpike]

For a lead water mains replacement - I'm planning on going from MDPE 25mm to HEP20 (under floorboards then up) to a new stop tap, then drain cock then more HEP20 onto the existing plumbing, which is 15mm HEP20.

Does it matter if the new HEP20 (either side of the new stop tap) is 15/22/25mm, considering that it reduces to 15mm when it meets the existing pipework?

I plan to duct and insulate under the floor boards and I realise I have to make sure I use the pipe inserts. I would go for copper but there's already plastic I'm not replacing and it'll be much easier to get the plastic 2/3m run under the ground floor.

I know you can get MDPE/HEP20 stop taps and joints but would I be better off using a standard copper stop and compression joints?

Cheers.

 

[John506]

There will be a bigger flow rate if you use a bigger diametre pipe before the stoptap.

I prefer brass compression.

Remember, you are not allowed to connect the pipe to the stoptap outside your property, you must have the water authority come out and do it.

 

[turnpike]

Thanks John,

Yeah they are coming in a couple of weeks to do their side of things.

Just realised I might as well stick with the mdpe until the stop tap (with ducting and insulation). Then 15mm copper until the existing 15mm hep20.

Is a standard compression 25 - 15mm stop tap the way to go, or should I look for one with an MDPE specific connector?

Any idea what tolerance mdpe has to bending? Is it ok to do a fairly sharp 90 degree turn?

 

[John506]

Personally just before the stop tap I would use an MDPE to copper pipe connector, then just connect the stop tap in 15mm copper, only about an inch or 2 of copper of course.

 

[John506]

And no don't bend it sharply as it may split or kink, use fittings.

 

[turnpike]

Ok cheers.. Good idea re: the short bit of copper before the stop, I plan to do that between the stop and the drain too.

Once the mdpe is in the house I need to send it along under the floor boards a couple of metres before surfacing. I assume you are suggesting I cut it and joint rather than having a bend in the mdpe. In which case, I might continue the 2m run in hep20.

 

[John506]

yes mate cut it and use an elbow

 

[turnpike]

Got it suppose I might as well use the mdpe for the 2m under floor boards. I think it's not designed for that but it will be ducted and insulated.

 

[John506]

You should be able to judge yourself wether it will kink, try and make it more of a slow bend and you may be ok, all adds to the water pressure after all.

 

[holty]

id go 25mm PE till the stop tap. then if in future unvented or so comes an issue you have the flow rate.thats if you have the pressure though.with mdpe its a bit versatile you can clamp it to stop the water.