pressure drop after installing compression stop tap

[smoleybaconfact]

I tried to install an exterior stop tap on my lead mains supply so I could turn off the water supply to my building. I have a shared mains, so I've been unable to turn the water off to my property without also turning off the supply to my neighbours. I dug down to find the lead main coming into the building, cut it and attached a universal adaptor to convert it to blue MDPE, installed a compression stop tap then installed another universal adaptor to change the MDPE back to lead. I used Plasson fittings. When I turned the water back on (from the street), I found that the water pressure in my building was badly affected. When I turn a tap on in the property the pressure is good for a few seconds and then drops considerably. My neighbours' water pressure was unaffected. I can't figure out where I've gone wrong. I noticed the Plasson stop tap had an arrow to indicate flow direction, I got that the right way round. I've turned the stop tap on as far as it will go. I was extremely careful when installing the pipes, but the only thing I can think of is that there's something stuck in the pipes. Any ideas?

 

[Bubblecraft]

Good chance something has lodged in the Pipe. I've also found that even new stop taps have a sticky gate. You should be able to feel it in the head when turning. I'd try a new stop tap first as finding anything lodged in the pipe may be difficult. Does the new stop tap only supply your property & is there a drop in size when you fitted the UTC or a drop in the MDPE?


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[smoleybaconfact]

the tap seems to turn really easily. The new tap supplies my property. However, Inside my property there is another tap that turns on another pipe which goes onto supply an adjacent building. This seems unusual, but they are commercial buildings. I guess the main building was built and then the adjacent one sometime after, running the pipe from inside the first was the easiest way to supply the second. I've only added one tap though - an outdoor one on the mains supply to my building. To make it clear, the pipe goes like:

street supply ---> tap on pavement --> block of flats --> back garden --> hole in garden and new tap I've fitted --> my building --> existing tap inside --> neighbouring building

 

[Bubblecraft]

Is the adjacent building effected, not your neighbours and the tap you fitted, does it still close & stop the supply?


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[smoleybaconfact]

the block of flats was unaffected. my building and the adjacent building now both have the same problem. the tap does close the supply.

 

[Bubblecraft]

Sounds like you may have something lodged in the pipe. You might be lucky & find something stuck in the UTC where it meets the lead going into your property. If the tap is shutting the supply, the gate should be working fine. The other thing that could cause the problem is a puncture in the lead underground after the UTC on the supply going to your property. With the many years of it down, the slightest movement in the pipe can cause it to crack. Is it feasible to replace the lead to your property?


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[smoleybaconfact]

well thanks, i'm going to undo the connections and have a look. It might be a crack in the lead, I was extremely careful to move it as little as possible but i might have cracked it. I could replace the run of lead but it would involve digging a 10m trench.

 

[Bubblecraft]

I completely understand. Honestly, it doesn't take much to puncture or crack lead. Even an inch can cause major damage. I had that problem in a flat when installing a bathroom. As the lead pipe ran under the floor from the kitchen, Covered in solid wood flooring, I couldn't replace it and so the only option was to re-supply the bathroom from the loft. Luckily it was top floor & had that option. Let me know how you get on. Hopefully you don't have to dig that trench!!


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[stani]

have you over tightened the connector, I used a similar connection and overtightened, this greatly reduced the supply pressure, try undoing a little and see if pressure increases.

 

[smoleybaconfact]

why does over tightening reduce the pressure? If it's crushing the lead, then won't the lead remain crushed even if you undo it a bit? I didn't realise you could over tighten them, I'm not sure how the seal around the lead actually works

 

[Phil]

You mention the arrow on the stoptap that indicates direction of flow, are you sure the water was flowing that way in the pipe?

From here its hard to picture the layout.

 

[Guest123]

I'd get a mini excavator, dig a trench and renew the whole lot.

 

[stani]

why does over tightening reduce the pressure? If it's crushing the lead, then won't the lead remain crushed even if you undo it a bit? I didn't realise you could over tighten them, I'm not sure how the seal around the lead actually works

have you actually tried slackening off a bit and then checked pressure, I've no idea what happened wether i had not got the pipe fully inserted (alkathene or lead) just know when i slackened off a bit the pressure increased, finished renewing all lead later on

 

[smoleybaconfact]

You mention the arrow on the stoptap that indicates direction of flow, are you sure the water was flowing that way in the pipe?

From here its hard to picture the layout.

it's the mains supply pipe that goes into the building so yes, I'm certain. It's the pipe that supplies my building, I cut a section of it out and installed 2 universal adaptors with a stop tap in between and now have reduced pressure.

 

[Plumb4fun]

Hi, the big clue is the fact that there is normal pressure for a couple of seconds, then drops off, this rules out any leak as any leak would not allow pressure build up, I would go for something got into supply pipe when you were working on it, (Does happen) pipe or fitting crushed somehow, or faulty stoptap, looks like you dont have a choice but to dismantle new fittings & examine.
ps as a possible easier way out can you not unscrew the head of the stoptap that you have fitted as this may give you a clue. Good Luck

 

[SimonJohns]

I would just say its due to the extra resistance of all the extra fittings.

If you are getting the oringal static pressure but the working pressure is reduced. Then the only reason for this is restriction in pipework

So yes you may have something stuck in valve. But my guessing. All the extra fittings and new stop valve is causing the drop in working pressure

 

[smoleybaconfact]

have you actually tried slackening off a bit and then checked pressure, I've no idea what happened wether i had not got the pipe fully inserted (alkathene or lead) just know when i slackened off a bit the pressure increased, finished renewing all lead later on

well I'll certainly give it a try! Can you explain why not having the pipe fully inserted into the the fittings would affect flow rate? I had to cut one section of the MDPE slightly shorter than the ideal length, so there is a chance it is not fully inserted into the second adaptor. I installed the first adaptor ('first' as in nearest to the supply, furthest from my building), a 15cm length of MDPE, then the stop tap, then attached the second adaptor to the lead and then had to connect this to the tap. For the final stage of connecting the 2nd adaptor to the tap with MDPE, I would have had to bend the lead on both sides a lot in order to fit the perfect length of MDPE pipe, so i cut it a bit short so I could get it in.


[building][----lead pipe][2nd adaptor][---MDPE pipe ---][stop tap][---MDPE pipe---][1st adaptor][lead pipe------][supply]

 

[SimonJohns]

well I'll certainly give it a try! Can you explain why not having the pipe fully inserted into the the fittings would affect flow rate? I had to cut one section of the MDPE slightly shorter than the ideal length, so there is a chance it is not fully inserted into the second adaptor. I installed the first adaptor ('first' as in nearest to the supply, furthest from my building), a 15cm length of MDPE, then the stop tap, then attached the second adaptor to the lead and then had to connect this to the tap. For the final stage of connecting the 2nd adaptor to the tap with MDPE, I would have had to bend the lead on both sides a lot in order to fit the perfect length of MDPE pipe, so i cut it a bit short so I could get it in.


[building][----lead pipe][2nd adaptor][---MDPE pipe ---][stop tap][---MDPE pipe---][1st adaptor][lead pipe------][supply]

What size mdpe 20/25/32???

 

[smoleybaconfact]

I would just say its due to the extra resistance of all the extra fittings.

If you are getting the oringal static pressure but the working pressure is reduced. Then the only reason for this is restriction in pipework

So yes you may have something stuck in valve. But my guessing. All the extra fittings and new stop valve is causing the drop in working pressure

the manufacturer stated that the tap would not affect flow rate, I didn't ask about the adaptors though. If some object did get in the lead pipe, then is my only option replacing the whole length of lead? I'm going to try attaching a length of MDPE to the tap and see if this produces good pressure, then it'll be clear it's the second adaptor or the lead pipe that is the problem.

just so it's clear this is the type of adaptor I used; [DLMURL="http://www.plasson.co.uk/main.asp?product_id=10212&cat=products&sCat=product&sel_nav1=16&sel_nav2="]Plasson UK[/DLMURL]

and the tap; [DLMURL="http://www.plasson.co.uk/main.asp?product_id=10238&cat=products&sCat=product&sel_nav1=18&sel_nav2=166"]Plasson UK Compression Fittings - Compression Fittings Valves[/DLMURL]

 

[smoleybaconfact]

What size mdpe 20/25/32???

25mm MDPE, the lead is 25mm as well

 

[SimonJohns]

the manufacturer stated that the tap would not affect flow rate, I didn't ask about the adaptors though. If some object did get in the lead pipe, then is my only option replacing the whole length of lead? I'm going to try attaching a length of MDPE to the tap and see if this produces good pressure, then it'll be clear it's the second adaptor or the lead pipe that is the problem.

just so it's clear this is the type of adaptor I used; [DLMURL="http://www.plasson.co.uk/main.asp?product_id=10212&cat=products&sCat=product&sel_nav1=16&sel_nav2="]Plasson UK[/DLMURL]

and the tap; [DLMURL="http://www.plasson.co.uk/main.asp?product_id=10238&cat=products&sCat=product&sel_nav1=18&sel_nav2=166"]Plasson UK Compression Fittings - Compression Fittings Valves[/DLMURL]

The tap will affect flow and working pressure

If you had 14lb lead and you've put a 20mm valve on there there will be a noticeable difference

 

[Bubblecraft]

Well that would rule out resistance regarding pipe. The UTC's & tap could be causing resistance though.


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[parsonsplumbing]

just check mains pressure at kitchen sink on cold side if its poor u might have to undo cold 1/2" nut and clear

 

[Joncpi]

I would first check the internal stopcock by removing the head. If that does not clear the problem then run a temporary PE pipe in from your new stopcock and check the pressure/ flow inside. If that improves the problem then it could be a partial blockage in the pipe. Use the temporary pipe to flush back down the lead service from the supply side of the internal stopcock to the outside.

However it is not a bad idea to replace the lead service. But there are alternatives to opening a trench. The pipe can be moled in. This means no reinstatement of any landscaping needs to be done as no trench is dug. However if the area is all grass then it is likely to be slighly cheaper to dig it by machine.

 

[smoleybaconfact]

joncpi, that sounds like a sensible plan. You are instructing to inspect the internal stopcock as you think that any blockage that got into the lead pipe is likely to have stopped there. Is that right?

 

[stevetheplumber]

thats the most likly place it will stop take the head of and run some water through into a bucket

 

[Joncpi]

joncpi, that sounds like a sensible plan. You are instructing to inspect the internal stopcock as you think that any blockage that got into the lead pipe is likely to have stopped there. Is that right?

Yes the most likely place for any debris to stop is up against the internal stopcock. But your service being lead and liable to corrosion inside the pipe and to deformation of the pipe in the ground by roots or by damage or by previous repairs, then a blockage can occur almost anywhere so even if there is no obvious problem at the internal stopcock then flushing back down the line can cure the problem. But I would still recommend renewal, maybe not just before Christmas though?

 

[smoleybaconfact]

thanks! it was something in the internal plumbing, so back to full pressure now. I didn't find the actual object but taking the stopcock off and putting it back on worked. I'm not sure if digging a long trench and replacing with MDPE is worth it. Why is mdpe better?

 

[Joncpi]

Lead is actually toxic so not good for you. If you live in a hard water area then there will be less lead in your water than if you have soft water. Lead is especially bad for young children. You could run the water for a little while before using it to clear any lead particles. The lead pipe does last many many years normally at least 100 but will eventually leak. MDPE is also good for at least 100 years or so they tell us. As I said you could look into moling or thrust boring to install a new pipe, rather than a trench.