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Discuss 20mm MDPE to 25MDPE (and 22mm Copper) in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Antony_0

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Hi all, we're doing some renovation work to our property and we wanted to install a sauna house (includes shower) in the garden, irrigation system and outside tap. I've ran a 25mm MDPE from the inside utility room where the main stopcock comes into the house. I originally thought that it was a 25mm MDPE coming into the house, but it appears to only be 20mm MDPE. The stopcock is only about a few centimetres away from the 20mm MDPE to 22mm copper pipe connection. I've attached a photo of where I imagine the new 25mm MDPE would connect to.

What I was originally going to do was move the stopcock down by 10cm or so, then insert an equal tee to the right, then back down through the floorboard, into the new conduit which runs to the garden. I have about 5 meters of 25mm MDPE left, so I was thinking I could do one of the following:

What I was thinking about now would be:

1. Move the stopcock down 10cm, buy a 20mm to 25mm "reducer" so that the pipe actually goes up in size and then I can use a 25mm tee that I had originally. The problem I'm not sure about is that the pipe in the space of 20cm would go from 20cm to 25cm back to 22cm (copper), so would that cause any flow issues?

2. Buy a 20mm to 25mm MDPE adapter, buy a 25mm stopcock, buy a 25mm MDPE to 22mm copper adapter and use that setup (similar to option 1, but the 20mm to 25mm adapter is put before the stopcock rather than after)

3. Buy some 20mm MDPE, move the stopcock down 10cm and use a 20mm MDPE tee which I could then keep the original 20mm MDPE to copper in place, but then upsize the tee on the right to attach to a 22mm MDPE to 25mm MDPE connector.

4. A completely different idea?

Sorry if that seems confusing. Many thanks in advance,

Antony
 

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ShaunCorbs

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You would need to move the existing stop tap down or take the new supply from the copper ?
 

Antony_0

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You would need to move the existing stop tap down or take the new supply from the copper ?
Hi Shaun,

The main water supply from the road comes from the MDPE pipe. I was thinking it would be easier to move the stop tap, but what I'm unsure about is any back pressure from going 20mm MDPE, 25MM MDPE then 22mm copper as I described in the original post. Is there a better way of attaching this new 25mm MDPE pipe?

Thanks,

Antony
 

ShaunCorbs

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Back pressure in regards to what ?

Below the stop tap install a 25mm tee (with two 20mm converters) and a 25mm stop tap vertically
 

Antony_0

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Back pressure in regards to what ?

Below the stop tap install a 25mm tee (with two 20mm converters) and a 25mm stop tap vertically
I was thinking about back pressure similar to when installing an air duct. If you go from 150mm down to 100mm, then up to 120mm I was told it makes it difficult for the air to come out because of the shape changing.

That makes a lot of sense, so the garden would essentially be on its own stopcock from the main feed?
 

ShaunCorbs

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You will be fine obviously if your pulling from the house the outside supply would reduce depending on your water main pressure etc

It doesn’t come into effect with a domestic supply only commercial

And yes
 

Antony_0

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You will be fine obviously if your pulling from the house the outside supply would reduce depending on your water main pressure etc

It doesn’t come into effect with a domestic supply only commercial

And yes
Thanks Shaun.

Today I started prepping for the 20mm tee which would then go onto a 20mm elbow, then the 20mm to 25mm adapter, then stopcock. The mains water MDPE pipe coming to the current stopcock sits inside a joist width of about 150mm and the next joist along has the 240L cylinder sitting on top of it. The MDPE fittings are quite bulky, so fitting the tee and elbow right next to each other so it's going to be tight to get that pipe down. I'm wondering if it's worth replacing the 20mm mains water MDPE in the basement and putting an adapter down there from 20 to 25mm along with the stopcock down there. I have around 8 meters of 25mm MDPE left so there's plenty to get down to the basement. That way it could feed the boiler and the garden.

Are there any restrictions on how far a stopcock has to be away from the mains gas and electric?
 

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