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No pressure in pressurised system


Shell820810

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We have just got the water on inside and apparently it just a drip! Not literally, but very very low pressure/flow.

 

We had a cowboy plumber at first fix. The legacy continues. New plumber said he should've tested it before putting in a pressurised system (reckons its the mains supply that is poor).

 

Downstairs cold taps are good pressure

Downstairs warm taps aren't good

Upstairs hot and cold are worse and gets even worse the longer it runs

 

Where do we start???

 

(Also had to dig up tiles and subfloor cos he mixed up hot and cold feeds).

Edited by Shell820810
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I don't think he really knows. The fact that the downstairs cold tap is ok , should that not mean the mains is OK and the problems within the house?

 

I have a video of the flow, but don't think I can attach videos?

Edited by Shell820810
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Also, do you know if you have an outside tap which comes directly off your underground water main? 

Can you ask next door if you can check their supply ( pressure and litres per min flow rate ). The communication pipe that serves you both / all will be at the same potential for you and next door, so best to eliminate / investigate from the supply inwards. 

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An actual plumber should be able to tell you better than me, and I don't really understand why your plumber can't tell you what is wrong.

 

There is a minimum required pressure for an unvented system, if you don't have that you need an accumulator tank.

 

A pressurised system should have a pressure vessel, often a small red tank next to the hot water tank. This should have a pressure gauge and allow you to top up the system. See if you can find it and look at the guage. It should be at about 2 bar.

 

Whenever our system has poor hot water pressure it is because there is a leak somewhere in the hot water system that has allowed the pressure to drop in the system. But like I say, surely this would be obvious to a plumber.

 

Nick is right, maybe people can help if they can see what you have.

 

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I'll get some photos tomorrow.  We have an outside tap and it seems to have good enough pressure too. We still don't have a decent plumber on the job, this fella was just into connect up a few taps, we weren't expecting this.

 

There is a very good plumber hubby works with from time to time that we could ask for advice but not sure we could get him on the job to sort it out.

 

Also, before we applied for the water connection I asked the neighbour about the water pressure, I didn't get any numbers, but they said it was fine, no issues.

Edited by Shell820810
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1 hour ago, AliG said:

A pressurised system should have a pressure vessel, often a small red tank next to the hot water tank. This should have a pressure gauge and allow you to top up the system. See if you can find it and look at the guage. It should be at about 2 bar

 

To clarify some details here further ;) 

A red pressure vessel would be non-potable, so would relate to the primary heating circuit. The pressure gauge on that would have absolutely nothing to do with the flow rate of hot or cold water within the property. The nominal pressure for a sealed HEATING ( primary ) system would be 1-1.5 bar. That pressure would be almost identical to the gauge on the system boiler as they'd be the same body of water. 

1 hour ago, AliG said:

Whenever our system has poor hot water pressure it is because there is a leak somewhere in the hot water system that has allowed the pressure to drop in the system. But like I say, surely this would be obvious to a plumber

 

Not sure what you mean here tbh. The dhw system is cold mains fed when you've got an unvented system. If you had a leak, it would hardly affect the terminal flow rate unless it was a torrent. A torrent is quite easy to find, so assume this can be ruled out. 

The pressure drop in a sealed heating system would only cause the boiler to switch off, and again, would leave the hot and cold flow rates completely unaffected. 

1 hour ago, AliG said:

There is a minimum required pressure for an unvented system, if you don't have that you need an accumulator tank.

 

You need to survey the mains before recommending an accumulator. If there is insufficient static pressure, the acc would never fill, at which point ( like my current job ) you'd have to fit a break tank, a cold mains booster pump, and then the acc. 

 

Any unvented install should have a 22mm cold mains 'backbone' running throughout the house. This job has a TS, so is in essence an instant water heater. This should also have a 22mm cold mains backbone ( all cold pipework done in 22mm bar the last outlet which can be in 15mm off the 22mm ), but should also either have the majority of the hot done in 22mm, or have radial plumbing ( individual runs of small bore to each outlet from a centralised manifold ) in order to alleviate resistance from the pipework and deliver maximum flow rates. From the pics, it's clear that the plumbing may well be mostly done in 15mm. 

@Shell820810, do you have pics of the hot and cold connections at the TS? Also, can your hubby conform how much 22mm hot / cold pipework, if any, has been installed, and to / from where ? Ta. 

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Nick,

Well I did say to ask a real plumber!

 

I had always assumed the red tank was part of the hot water system. Quite a few times we have had worked done on the house and ended up with a leak which took the pressure down to zero. I hadn't realised, but they had always been in the heating system. I think we probably then had hot water issues because the lack of pressure stopped the boiler working. I stand well corrected. Probably shouldn't have replied as I was uncertain about it.

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Slightly off track but is that the way it's done normally ref running pipes in the floor? I mean the way the PIR has been roughly channelled then normal pipe insulation used? My goto not knowing otherwise was to carefully V everything and replace when the pipes were in then foil tape over the top:

 

SAM_3493

 

Edited by Onoff
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Just want to echo what others have said. Get the main surveyed for pressure and flow rate (these are different things) near the main as possible and at the house. Only with that data can you start thinking about solutions. If the static pressure is good but flow rate is poor then the an accumulator/bladder tank might be an option but don't rush that decision without data. 

 

 

 

 

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Just checked the outside tap, two 25l drums almost filled in 1 minute.  Will check on pipe sizes and stopcock. The pressure gauge has been taken off, it was only on when first fix plumber was testing for leaks.

 

Material list attached with quantities of pipe sizes etc

20161002_093126.jpg

Edited by Shell820810
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o.O 50 litres per min flow rate is great. 11/12 is average, 20 is good. :)  

Can we have some pics of the TS and peripheral plumbing plz. Does the cold go onto the TS in 22mm pipe? 

Also, do you know if plumb-o-nugget fitted a pressure reducing valve? If so, that's the first place to look for increasing the flow. I went to a job where they had 10 bar incoming mains, it was like a fire hydrant. The original installer had fkd up and didn't put the PRedV in the right place so the UVC expansion popped and flooded their £1m house from upstairs down :( 

I rejigged the plumbing and fitted a secondary PRedV at the stopcock and it was factory set to 3.5bar. I put a gauge on so the customer had a confidence register to assure them it was working fine, and I left them to it. I had a phone call from them saying that they were getting very low flow to the kitchen sink and showers so could I come back. I found the PRedV was strangling the flow more than it should have ( 22mm valve ) so I increased the pressure to 4 bar. This made a huge difference and they were pretty much as good as before I turned up so I'd deffo look there. 

Buy a gauge and stick it on the bath tap cold connection. With the hot running very slowly ( no pun intended ) adjust the PRedV very slowly and allow a few seconds for it to alter and equalise. Hopefully it will be as simple as this. ;)  

If there one and it's set at 3 bar, try at 3.5, and if it's set at 3.5, try at 3.8 first. Raise incrementally until your happy with the flow but don't go too high. 

We still need to know the pressure off the outside tap tbh. 

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