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Dripping Hot Water Taps When Boiler on (Read 862 times)
rampaging_haggis
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Dripping Hot Water Taps When Boiler on
Feb 14th, 2021, 9:16am
 
Hi gents,

Bit of a strange one... asked a couple of plumbers met with a bit of puzzlement so turning to online and hopeful you guys can help.

We have dripping hot water taps and shower all over the house. Shower is the main problem as it isn’t a small drip. This only seems happens when the boiler kicks in and starts to heat the water - standard boiler with a hot water tank and pressure vessel.

I’ve changed out washers in shower (they are old gummers sirrus valves). Maybe improved slightly but still lots of dripping. Taps drip too so not convinced it’s just an old shower / one tap issue.

I can only imagine the increased pressure when the water gets hot it causing this.

Anyone got any ideas?

Cheers,

Calum
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thescruff
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Re: Dripping Hot Water Taps When Boiler on
Reply #1 - Feb 14th, 2021, 11:28am
 
let's start with the boiler,

Standard boilers don't exist, so make and model, please.
Is there a pressure gauge and what does it read before and after the boiler is running?

Cylinder, type please, is it an unvented cylinder, or do you have a storage tank somewhere.
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rampaging_haggis
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Re: Dripping Hot Water Taps When Boiler on
Reply #2 - Feb 20th, 2021, 7:32am
 
Thanks for getting back thescruff!

Boiler is a Worcester Bosch Greenstar 8000 35kw (been in less than a year) and the pressure guage reads 25.5 consistently irrespective if it’s working or not.  The other gauge above the expansion vessel which reads about 0.8 bar cold and around 1 bar when the water has been heated. It’s an unvented system.

Cylinder is a mega flow heatrae sadia.

Cheers
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Re: Dripping Hot Water Taps When Boiler on
Reply #3 - Feb 20th, 2021, 7:33am
 
Should have also said - there’s no colt water tank in the loft.
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thescruff
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Re: Dripping Hot Water Taps When Boiler on
Reply #4 - Feb 20th, 2021, 12:14pm
 
The expansion vessel is it white or red?

what is the unit for 25.5 it's normal in bars?

Is the boiler the life system?

Is the whole system the same age including the taps etc?

If the taps etc are older, what system was in place prior to the new boiler.

Silly question, what is the make/model of the taps and shower?

Is the cylinder a replacement for an unvented cylinder?

Is there any discharge from the pressure valves Cylinder or boiler?
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« Last Edit: Feb 20th, 2021, 12:16pm by thescruff »  
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Re: Dripping Hot Water Taps When Boiler on
Reply #5 - Feb 20th, 2021, 5:32pm
 
Expansion vessel is red

The reading is 25.5 bar on the boiler......? Never seen this change - can’t be correct surely. Reading above the expansion vessel is 1

Yes, it’s the Greenstar 8000 life system

Only moved in 18 months or so so assuming the system and all taps are the same age -2004. We’ve only changed the boiler (original was a 22kw potterton) was certainly the original.

Can’t see the make of any of the taps but the shower is a sirrus calvus. I’ve changed the washers in this once which improved things but didn’t solve them.

We’ve certainly not replaced the cylinder - only the boiler.  I have just noticed that it says max mains pressure is 16 bar though....!

No discharge from either relief valve.
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Re: Dripping Hot Water Taps When Boiler on
Reply #6 - Feb 21st, 2021, 11:37am
 
Can you check it isn't 2.55 or anything other than pressure? if not get the installer to check it out under warranty. The boiler pressure should be around 1-1.3bar when cold. if however, it is 25.5 bar the boiler wound be scrap.

The red vessel should be reading 1-1.3bar when cold.

Ok back to the problem, do you know how to re-charge the cylinder? it will be in the manual and quite simple to do. normally you would get a discharge when they lose there charge but may be worth trying.

Have you any way of checking the mains and hot water pressures?

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Re: Dripping Hot Water Taps When Boiler on
Reply #7 - Feb 21st, 2021, 11:40am
 
The post you deleted could be important being an unvented cylinder.

Can you post a pic of the dent, please?
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Re: Dripping Hot Water Taps When Boiler on
Reply #8 - Feb 21st, 2021, 1:39pm
 
Thanks for your help with this - it is appreciated.

Pressure definitely reads 25.5 bar. The user manual mentions it as 'system pressure'. Manual mentions what to do if the system has low pressure but doesn't say anywhere about the system having pressure which is way too high....! I would have assumed a relief valve would have opened or the boiler would shut down to protect itself if the pressure was actually 25.5 bar wouldn't it?

I've put pictures in below of this and of the dent on the cylinder (after posting though.

Will certainly try recharging the cylinder. Don't have a way of checking the water pressure right now unfortunately but more than happy to purchase something if you think it might help. All I can say just now is that the water pressure for both hot and cold seems quite high all over the house.

Also just stuck a picture of the technical specs of the cylinder if that helps at all.

Image 1Image 2Image 3
Image 4Image 5




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Re: Dripping Hot Water Taps When Boiler on
Reply #9 - Feb 21st, 2021, 5:42pm
 
I would get the engineer back under warranty. something isn't right that needs fixing although I doubt it really is 370 ish PSI.

The dent looks like some leaned against it when they were working the cupboard, maybe put a pair of steps against it when they fitted the expansion vessel.

Ask the engineer if he is qualified to work on the cylinder, he may have the kit to test the hot and cold pressure as well.

Where are you roughly?
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Re: Dripping Hot Water Taps When Boiler on
Reply #10 - Feb 21st, 2021, 6:15pm
 
Border between South Lanarkshire / Scottish Borders. Really appreciate the help mate thanks. 👍
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Re: Dripping Hot Water Taps When Boiler on
Reply #11 - Feb 22nd, 2021, 8:22am
 
A bit far away.

Thinking it would be an idea to phone Worcester about the boiler.

Back to the problem, Can you post a pic showing the right-hand side with as many pipes as possible, special interest in the cold feed to the cylinder and the pressure reducing valve.

Note if you re-charge the cylinder it's likely the pressure relief valve will drip and will probably need replacing.

We need to find out the mains pressure, a call to your water supplier will tell you what it should be (average)

Another job you can do, is fill a bucket with a known volume and time how long it takes, do the hot and cold separately. Ltrs/Mins
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Re: Dripping Hot Water Taps When Boiler on
Reply #12 - Feb 22nd, 2021, 12:05pm
 
Phoned Worcester Bosch and they have said that the boiler pressure is fine. Apparently because it isn't a system or a combi boiler the pressure sensor is essentially not connected so the reading is obsolete.

The boiler is due it's service next month anyway so will ensure then that the engineer is happy with this too.

Results of the water test:

Cold Feed - 33 litres per minute
Hot Feed - 21 litres per minute



I've posted another album with as many pictures as I can think might be useful....

Image 1Image 2Image 3
Image 4Image 5Image 6
Image 7Image 8
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Re: Dripping Hot Water Taps When Boiler on
Reply #13 - Feb 22nd, 2021, 2:14pm
 
Looks like a good job.

Did you do the pressure test at the kitchen sink? which would account for the difference. ( you have a balanced system so the pressure difference should be minimal)

How old are the taps?
Has it always been a pressure system or could the taps be low pressure for an open vented system?

The only thing I can suggest at the moment is to re-charge the cylinder.
The only other mechanical fault is going to be the pressure reducing valve, you can buy new cartridges, but my advice would be to ask the service guy if he is qualified for unvented cylinders and maybe bring the boiler service forward to look at the cylinder at the same time.
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