Moonshine Posted August 12, 2021 Share Posted August 12, 2021 I have a bit of an odd arrangement of the water supply into my build. The basement where water is to come into is on block and beam from earth, as per the marked up drawing below The waterpipe externally is going to come from under ground to penetrate the outer wall, into a cold space and come up through the block and beam to the stop tap under the stairs. I am about to put the block and beam down in this area, and have the penetration to the outer wall done. I need to understand how to treat the water pipe under the block and beam, especially as I am not ready for the water pipe to be laid yet. Shall i run a duct from the hole in the front wall to the hole in the block and beam for the water pipe to run through when its time for it to be installed, if so what size duct? I presume that the waterpipe in the cold space under the block and beam will need to be insulated to stop it freezing, if so how to do this when its to be run through the duct, what thickness of insulation? What diameter of pipe to use for the water supply? Link to comment Share on other sites More sharing options...
markc Posted August 12, 2021 Share Posted August 12, 2021 Interesting detail, I think I would be installing the duct as you say and then insulate the pipe as it is installed through the duct. .. 25mm pipe with 70mm dia insulation will go through the duct if you keep the bend radius as large as possible Link to comment Share on other sites More sharing options...
Moonshine Posted August 12, 2021 Author Share Posted August 12, 2021 14 minutes ago, markc said: Interesting detail, I think I would be installing the duct as you say and then insulate the pipe as it is installed through the duct. .. 25mm pipe with 70mm dia insulation will go through the duct if you keep the bend radius as large as possible what diameter of ducting are you thinking? Link to comment Share on other sites More sharing options...
markc Posted August 12, 2021 Share Posted August 12, 2021 7 minutes ago, Moonshine said: what diameter of ducting are you thinking? 100mm Link to comment Share on other sites More sharing options...
PeterW Posted August 12, 2021 Share Posted August 12, 2021 Use 110mm underground drainage with a rest bend and bring it up through the floor. If it ever needs to be replaced then it’s dead simple. 1 Link to comment Share on other sites More sharing options...
Temp Posted August 12, 2021 Share Posted August 12, 2021 (edited) 5 hours ago, markc said: Interesting detail, I think I would be installing the duct as you say and then insulate the pipe as it is installed through the duct. .. 25mm pipe with 70mm dia insulation will go through the duct if you keep the bend radius as large as possible Could put the insulation on the outside of the duct if you can be sure it won't flood and float. How about filling part of that void with 500-750mm mm gravel so it's effectively buried. Edited August 12, 2021 by Temp 1 Link to comment Share on other sites More sharing options...
Oz07 Posted August 13, 2021 Share Posted August 13, 2021 Water board should advise you on supply size. Round here they want 32mm for anything above 3 beds. Not sure how strict that is. You can get preinsulated duct with mdpe already in. I'd honestly consider this in your arrangement. The water board are the worst for failing round here anything they can think of. If your void will be accessible when water is inspected there's a lot less risk. If your b&b will be insulated and screeded prior to sign off go with belt and braces approach above. Link to comment Share on other sites More sharing options...
Moonshine Posted August 13, 2021 Author Share Posted August 13, 2021 2 hours ago, Oz07 said: Water board should advise you on supply size. Round here they want 32mm for anything above 3 beds. Not sure how strict that is. You can get preinsulated duct with mdpe already in. I'd honestly consider this in your arrangement. The water board are the worst for failing round here anything they can think of. If your void will be accessible when water is inspected there's a lot less risk. If your b&b will be insulated and screeded prior to sign off go with belt and braces approach above. looking into it South west water standard is 25mm, they actually have this little diagram to show the arrangement. i think that i am going to use a twin wall duct, internal diameter of 94mm which should give me enough flexibility to feed the insulated water pipe though, i won't seal the external wall hole so that there will be some flex to feed the pipe through. even with the longer turn radius i think that the rest bend will be tight to get through 1 Link to comment Share on other sites More sharing options...
Moonshine Posted August 13, 2021 Author Share Posted August 13, 2021 This is the area it's going to run under, (dpc to go in under the beams). There is a hole in the external wall to the right hidden behind a beam Link to comment Share on other sites More sharing options...
PeterW Posted August 13, 2021 Share Posted August 13, 2021 Use 25mm MDPE and sleeve it with 28x19 armaflex pushed over the top of it without splitting it. Fits easily inside 110mm UPVC 2 Link to comment Share on other sites More sharing options...
Dave Jones Posted August 13, 2021 Share Posted August 13, 2021 5 hours ago, PeterW said: Use 25mm MDPE and sleeve it with 28x19 armaflex pushed over the top of it without splitting it. Fits easily inside 110mm UPVC no use 32mm its same price. The water supplier will tell you exactly what they require you to do and will inspect that you have done it prior to connecting you. Link to comment Share on other sites More sharing options...
PeterW Posted August 13, 2021 Share Posted August 13, 2021 No don’t. 32mm is only used in exceptional circumstances for runs over 100m and where pressure is low so you need an accumulator. ST and AW do not specify the insulation level - it just says “insulated” in the specs. Nitrile rubber is more flexible and around 25% better insulator but unless there are multiple air bricks and a flow of air below the floor you will not have a frost risk. 25mm will do 46.8l/min at 75% velocity but it’s unlikely you will have the pressure to do that. Link to comment Share on other sites More sharing options...
Moonshine Posted August 17, 2021 Author Share Posted August 17, 2021 On 13/08/2021 at 16:39, PeterW said: 25mm will do 46.8l/min at 75% velocity but it’s unlikely you will have the pressure to do that. actually we have really high pressure in the existing house, and we were recommended to put a pressure reducer in to the new build. Link to comment Share on other sites More sharing options...
PeterW Posted August 17, 2021 Share Posted August 17, 2021 Even more reason to go 25mm and then use a PRV on the inlet down to 4.5 bar then use a control set to get to 3 bar for the UVC Link to comment Share on other sites More sharing options...
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