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mains water - how to bring it in and up through slab


MarkH
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I'd like to run the slightly vague ideas I have past the forum-mind:

How do you bring in mains water through your wall(s) and up through the slab? My hazy idea is that I run the blue alkathene through a suitably lintelled hole in my (solid, 215mm) wall, sleaved in 110mm soil pipe that is in turn surrounded by 'pea gravel'. Then presumably the alkathene is directed up through the slab to a stopcock (under the kitchen sink in our case, just the other side of the wall). Does the pipe run un-sleeved up through the slab concrete? How is airtightness maintained?

I'm a bit clueless here, all info gratefully accepted.

 

Edited by MarkH
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A ran my blue mdpe water pipe inside 68mm twin wall flexible blue ducting that appears to be made for the job. but plenty do put it in a bit of drain pipe.

Used the same twin wall in black for the electricity supply.

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For the issue of airtightness, just picture the pipe going down through the duct to the ground, and then as it exits the duct the pipe is surrounded with compacted fines ( dust ) which will be wet. That'll stop just about any movement of air between the house and the atmosphere ;)  

Do NOT squirt expanding foam down the soil pipe to 'plug' the hole as it reacts with alkathene / mdpe and is a big no no. 

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6 minutes ago, Nickfromwales said:

 

Do NOT squirt expanding foam down the soil pipe to 'plug' the hole as it reacts with alkathene / mdpe and is a big no no. 

I didn't know that ...! I was pretty sure that the foam was inert but obviously not ..!

Every day is a school day .! 

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Normal isocyanate/urethane moisture curing gun foam does not react with MDPE at all.  It contains no solvents or other agents that attack polyethylene, in fact the solvents that do attack foam (MEK and acetone) are supplied in polyethylene containers specifically because they do not attack this particular polymer.  All gun foam now sold is solvent-free (hence the reason that even kids can buy it).

The same is not really true for PVC or ABS, both of which can be attacked by solvents used to clean gun foam (but not the foam itself).  EPS will cause PVC to go brittle by promoting the leaching of plasticisers so must not be allowed to come into contact with stuff like PVC insulated cable, but is fine against MDPE.

As a general rule MDPE (polyethylene) is highly resistant to practically every organic and inorganic solvent in common use.  It even resists toluene.  The only solvents that do attack it (but only cheap LDPE containers, by making it brittle , not MDPE or HDPE) are petroleum based solvents, so it's not advisable to store petroleum, benzene etc in LDPE containers or allow it to come into contact with LDPE pipe (not commonly found in water systems, but it is sold by people like John Guest for air systems).

Sorry you got bum info, Nick, but my first degree was chemistry, specifically organic chemistry.

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Point the Welsh Water guy in my direction next time, Nick, I'll give him some pain and grief to make up for giving you bum info..............

To be fair, there were some solvent-containing foams around many years ago, but mainly the two pack stuff, rather than the moisture curing gun foam.  They don't attack MDPE, but some solvents can penetrate the pipe and potentially contaminate the water.  However, we're talking about minuscule amounts of solvent that were only around very briefly when these older solvent-containing foams were liquid.  Once cured the solvents would have dissipated and the contamination risk, very tiny as it was, would disappear.

One problem when regulatory bodies start looking at potentially harmful volatiles is that they often fail to take account of their volatility, and make false assumptions about their potential to linger.  The worst are all the fear-mongers that keep spreading scares about formaldehyde.  The stuff is highly volatile, it evaporates so fast that it just doesn't stay around long in anything that's not very well sealed.

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7 minutes ago, joe90 said:

Is it necessary to run the blue water pipe in a duct? What's the lifespan of the stuff?

Yes, so in 60 years time when you are in OnOff's position, you don't have to dig up the house to pull a new pipe through.

I found it ammusing when my road crossing was done, I put in a duct for my electricity and telephone cables, but Scottish Water burried THEIR pipe directly in the soil in the bottom of the trench, not even in sand.

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53 minutes ago, joe90 said:

Is it necessary to run the blue water pipe in a duct? What's the lifespan of the stuff?

It's pretty much bombproof tbh, but it's the criteria set out by the water authority that dictates the way it's pulled in in most circumstances. 

700-750mm below ground, 4" duct / sleeve of non aggressive material, then the stopcock, then a non-return ( double check ) valve and a drain off cock. Anything less and they refuse to connect you down here. 

Always remember that the WB will want YOU to excavate the foundation of the boundary wall, and will ONLY dig OUTSIDE the boundary. Your pipe needs to have a good bit of slack and be free to pull under the boundary wall at said depth. 

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Thanks guys. Well I am in the situation of already having a connection so don't have to worry about what the water company want, but good to know what is the gold standard regarding this.

Edited by joe90
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 I'll have about 50m of galvanized iron pipe doing nothing soon! xD

Cheers @ProDave, the original barstewards just buried my pipe in the clay, No shingle, nothing.

I think my water company says 750mm min / 1350 max depth and to be ducted where it enters the building. 

The MDPE's cheap enough the ducting unless I've been looking in the wrong places is more expensive?

What's the norm, internal diameter wise, for a duct to run a 25mm MDPE in, anyone?

Edited by Onoff
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3 minutes ago, Nickfromwales said:

I wouldn't go less than 70-80mm, but as you've prob got off cuts of soil, use that with a long radius bend. 

I think Dave is getting at running the MDPE in duct for the WHOLE LENGTH of the run.

With what I want to run cable/pipe wise under the garden it won't be cheap I know that!

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  • 3 years later...

I found this old thread via a Google search and my question is related so I thought it would be ok to tack this question on here.

 

Question: In a more recent BH thread someone mentioned that blue MDPE should not come into contact with concrete because of the risk of a chemical interaction. Is this true?

 

I do understand the related issue of a pipe freeze risk due to such contact. 

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19 minutes ago, epsilonGreedy said:

I found this old thread via a Google search and my question is related so I thought it would be ok to tack this question on here.

 

Question: In a more recent BH thread someone mentioned that blue MDPE should not come into contact with concrete because of the risk of a chemical interaction. Is this true?

 

I do understand the related issue of a pipe freeze risk due to such contact. 

You'd be right. If we need to encase PE pipes, we normally insert in to a steel sleeve or wrap in a plastic liner before pouring. In a domestic situation, bring the pipe up through a pvc pipe.

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Don't know where the idea that MDPE is attacked by concrete came from, but it's completely false. 

 

The only reason for putting a water pipe in a duct, rather than directly embedded in concrete would be if the water regs requirement for the pipe to be "accessible" was being enforced by someone who was absolute stickler for the meaning of "accessible".   Having said that, I ran ours inside a bit of 50mm duct, just in case it ever needed to be replaced.

 

 

 

 

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Had to drill through the existing footings when I renewed my mains water. What a bitch! There's a metre of pipe insulation down inside the duct and Wiska gel on top to hopefully fully seal the duct.

 

tb

 

 

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10 minutes ago, JSHarris said:

Don't know where the idea that MDPE is attacked by concrete came from, but it's completely false. 

 

 

Pleased to hear this. My own hunch was that chains of plastic polymer molecules are unlikely to be troubled by a little alkaline in cement. I am far more worried by four legged furry creatures with sharp teeth and a proven interest in plastic.

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