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