JohnMo Posted April 30 Share Posted April 30 Or Following this https://www.pandhengineering.co.uk/advice/pressure-loss And use this data sheet for MCL pipe and fittings Uponor-s-press-plus-technical-data-sheet.pdf Link to comment Share on other sites More sharing options...
Spinny Posted April 30 Author Share Posted April 30 Not sure that is the right approach though, it is the flow rate through the total pipe length I want to know not just a pressure drop. If you replace a section of a hose pipe with a straw, I rather think it will drastically reduce the flow rate through the hose. Even if the straw is only a few cm long. Link to comment Share on other sites More sharing options...
dpmiller Posted April 30 Share Posted April 30 have you decided this is a problem without actually seeing an issue? Restrictions at the tap or shower will reduce the effect of the connectors... Link to comment Share on other sites More sharing options...
JohnMo Posted April 30 Share Posted April 30 On 29/04/2024 at 06:59, Spinny said: also have flow problems on the UVC where the pressure falls from 3bar to 1.4bar when a tap is turned on. This despite supply being 3.5bar and 20l/m. Where are you measuring this? Has the issue always been the same? Most likely nothing to do with the pipe used. Upstream or down stream of the cylinder. My UVC is piped in 22mm Hep2O upstream of the UVC and then in 16mm pert-al-pert pipe with a 14mm bore or less, pipe run at longest is 20m and have zero flow issues. When you enter the tap the bore size will drop to around 6 to 8mm, they will also have built in flow restrictions to limit flow rate also. Your straw analogy - water velocity would simply increase and then return to normal after the restriction. The restriction would rob a very small small amount of pressure head. Link to comment Share on other sites More sharing options...
joe90 Posted April 30 Share Posted April 30 Where is @Nickfromwaleswhen you need him 🤷♂️ Link to comment Share on other sites More sharing options...
Spinny Posted April 30 Author Share Posted April 30 1 hour ago, JohnMo said: Your straw analogy - water velocity would simply increase and then return to normal after the restriction. The restriction would rob a very small small amount of pressure head. It isn’t just pressure though it is flow rate. When a tap is turned on the shower flow drops by up to half. The way I am thinking of it the system is like a balloon. If you let water out of it faster than it can flow in then the pressure in the system will drop and you will never get more flow rate out than you have coming in. I can get 20l/m from an outside tap on 15mm copper direct from the mains. But I only get about 12l/m total from outlets downstream of the UVC and MLC pipe. Something is choking off the flow. Back to the straw analogy, all points in the pipe must have the same flow. Yes the velocity will be higher in the straw section. But the question is will the straw section reduce the flow through the pipe. Intuition and practical experience says yes it will, otherwise we wouldn’t have 6-12inch water mains under the road we would have straws. Put a nozzle on a hose pipe and you increase the velocity at the nozzle but you still reduce the flow rate through the pipe. Link to comment Share on other sites More sharing options...
JohnMo Posted May 1 Share Posted May 1 Your outside tap is connected to main water, and you get 20l/m, ideally you could also do with pressure measurement on the main to compare the pressure change with no water being run out of the tap and 20L/min coming out of the tap. To compare the dynamic and static pressures. This will give you a known point to start from. Your balloon is the water main in the street, the straw is the pipe from the water main in the street to the house. That is the first point to test, to see what happens. The mains water pressure at peak times should be a minimum of 1.5 bar dynamic pressure - so pressure when your outside tap is fully open. If its lower than this you will have flow issues, no matter what pipe you use and it is mains supply rate / pressure that is the issue. Start there to confirm all is ok at the inlet end. Link to comment Share on other sites More sharing options...
dpmiller Posted May 1 Share Posted May 1 so what kind of PRV is before the tank? Some have a fair bit of restriction- even before the strainer gets clogged... Link to comment Share on other sites More sharing options...
jayc89 Posted May 1 Share Posted May 1 On 29/04/2024 at 11:00, joe90 said: Whilst I feel sorry for you and your situation which is very wrong, not all builders are like this, I had a brilliant builder and no complaints at all, it was not luck I searched using customers recommendations to find him. I've spent months waiting for the builder I want to do some structural work. Whilst it's been frustrating having to live with parts of the house unfinished, it'll be well worth it in the grand scheme of things, IMO. Link to comment Share on other sites More sharing options...
Spinny Posted May 1 Author Share Posted May 1 OK I will do some more measurements. I am quite prepared to pay to replace the lead mains pipe. However this will take weeks/months to achieve. Meanwhile this stops internal works progressing because if the mains is upgraded but makes no difference, the MLC pipe will then have to be replaced. The later this occurs the more flooring and finishing will have to be ripped up to achieve it. I am not risking £1000’s on hearsay that the 25mm MLC pipe and its 14mm ID connections will provide 30l/m flow. I need to know now ish if this MLC pipe is an inadequate throttle point as I suspect. (I have already had another plumber advise that the MLC connectors are a real problem and must be replaced. Press fit connectors have been used on the rad pipes downstairs too and all the rads will not heat up. Copper pipe on the rads upstairs and they all heat up fine.) Link to comment Share on other sites More sharing options...
dpmiller Posted May 1 Share Posted May 1 how many kW are you pushing through the rad pipes? Link to comment Share on other sites More sharing options...
Spinny Posted May 1 Author Share Posted May 1 12 minutes ago, dpmiller said: so what kind of PRV is before the tank? Some have a fair bit of restriction- even before the strainer gets clogged... Builders plumber started by saying the PRV could be a problem but he has now replaced it but it has made no difference. Gledhill PRV has been replaced with a Caleffi PRV. Plumber claimed the old PRV would be returned and tested for faults. But I never saw it as he must have whisked it out and hidden it in his van - perhaps he didn’t want me to see it wasn’t clogged. I rather doubt anyone is going to test a £30 part for faults! He also couldn’t get offsite fast enough. Link to comment Share on other sites More sharing options...
Spinny Posted May 1 Author Share Posted May 1 9 minutes ago, dpmiller said: how many kW are you pushing through the rad pipes? I’ll check, but it is 4 rads, 2 standard rads, one 3 column rad, one 2 column rad. Nothing bigger than 600 by 900. Plumber has been to rebalance them 3 times now. The last time he has been dishonest and turned up the boiler to 65 without telling me to try to escape the fact the rad pipework must be a problem. Link to comment Share on other sites More sharing options...
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