Worcester Bosch 35CDi II losing pressure constantly

[mlynn1974]

Hi all,

This is a first long post but please read on.

First of all we have had major building work at the house due to storm damage in November 2009. We are still living in temporary accomodation and not living at the property until everything is repaired and our furniture is returned from storage.

We have a Worcester Bosch 35CDi II installed in September 2006 by the previous owner. It is a 2 storey house with the boiler located downstairs.
We have Scottish Gas HomeCare 400.

In February 2010 underneath the boiler there was a cold water drip leak coming from a big compression joint. A plumber tightened it up and the boiler ran fine with no visible leaks. No pressure loss was noted.
Another plumber said later that it is part of the diverter valve.

We had a mixture of old copper pipework downstairs, a bit of plastic pipework in the kitchen and microbore upstairs.
The builders found that the upstairs tail pipe ends were leaking so the system was switched off and drained down in March 2010 and not repiped until October 2010.

The system was recommissioned with Hep2O barrier pipe upstairs, 4 new radiators (because the builders lost the old radiator brackets), new lockshields and new TRVs on 13th November 2010.

The boiler was given an initial inspection by Scottish Gas on 19th November 2010. He checked the expansion vessel, electrical safety, gas emmision at the flue etc. All OK. The system ran fine for 1 week at 1.5 bar.

On Friday 26th November 2010 the pressure was noted to be 2.2 bar which I thought was too high but I thought maybe the builder had topped it up after bleeding one or more of the radiators. I remember this because it started snowing outside and it was really cold outside.

On Saturday 27th November 2010 the pressure was at 0.8 bar which I know was too low. I contacted the builder who advised how to top it up using the filling loop key\grey button to 1.5 bar. The boiler lost pressure every day thereafter.

In general the system pressure went down from 1.5 bar to 0.8 while running continously for 12 hours. It lost more pressure when it was switched off and cold.

Scottish Gas visit 1: 1/12/2010
The engineer checked the charge on the expansion vessel. It was "a bit low". It was topped up expansion vessel to 1 bar. The system was repressurised to 1 bar cold.
Replaced PRV.

The system drain pipe was inspected and a big icicle from the PRV drain pipe suggested that the PRV was passing water and\or stuck open.
The system still kept losing pressure.

Scottish Gas visit 2: 2/12/2010
The engineer tightened a few compression joints on the boiler. He check the Schrader Valve and expansion vessel pressure again (both were OK)
and looked under the floor boards upstairs but found nothing.

Scottish Gas visit 3: 3/12/2010
The engineer ran a boiler isolation test. The boiler was isolated for 7 hours, then he came back. The pressure dropped in seconds after being reopened. This showed that there is likely to be a leak on the system, not the boiler. He didn't have any leak sealant and his boss didn't like using it on "leaks of this size", so he left and asked me to book another
appointment when he would come out with some leak sealant.

Scottish Gas visit 4: 8/12/2010
The engineer ran Salamander leak sealant through the system. No change.

Scottish Gas visit 5: 14/12/2010
The engineer inspected under the floors downstairs but no leak was found.

Scottish Gas then gave me a quote for repiping downstairs.
They said it would take 3\4 visits to cut and cap downstairs into zones to test each bit individually but I couldn't take the time off work for all that.

The system pressure held at 1.5 bar for 5 days 23-27th December. Maybe the leak sealant worked for a while.
I bled one cold radiator upstairs and topped up the boiler again.
The pressure loss came back.


Scottsh Gas then have me a quote for a downstairs repipe but then said they couldn't do it until the end of January\start of February
because all the engineers in the area are working on maintenance, not upgrades! They advised that I could get a local company
to repipe downstairs. It wouldn't break the HomeCare agreement "if it was done properly". I got a couple of quotes and went
with a big local company who could come in at the start of January.


We were repiped in copper downstairs on 10/1/2011 and they got rid of a lot of mess e.g. pipes running up the corridor then back down to a radiator and bits of Hep2O in the kitchen. They worked well and the system doesn't creak when warming up now.

- They didn't repipe a bit in the bathroom to prevent lifting tiles.
- They found a leak in the small living room at a corner joint literally 2 feet away from where Scottish Gas looked.
- They fitted all new pipework and lagging, new TRVs, new lockshields and ran a cleanser and inhibitor through the system.
- They ran a pressure test at 3.2 bar for 1 hour with no problems then lowered the pressure to 1.5

The pressure dropped to 0.8 within 4 hours of them leaving.

The system is now losing pressure down from 1.5 bar (hot) to 0.3 bar every 8 hours so I top up and run the boiler from 7:30pm - 11pm and
8:30am - 9:30am to keep the house warm when I come home and before I go to work.

The heating engineers came back on 17/1/2011 and lifted the tiles in the bathroom to check there, they inspected every pipe and every joint they fitted downstairs and found no leaks on the pipework when running (hot) and when the system was switched off (cooling down).


My questions are:
The boiler or system still loses pressure when filled to 1 bar cold and the heating is left off.
Where does the water go? Does it fill the pipes downstairs?
I don't know about plumbing but surely it can't go upstairs without the pump running?

I have noticed drips below the boiler but it is not coming from the big compression joint tightened in February 2010. It doesn't seem to be coming from the filling loop key area because I dry the little basin I put below it every time I fill it. It is more than a couple of drips you get by removing the filling key, maybe 20-30ml of water.

I have several worries:
1. There is a leak upstairs requiring laminate flooring to be lifted,
2. It is in the pipe chase that goes upstairs,
That is the only bit of original pipework left in the house but there are no drips at the bottom of the pipe chase.
3. Could it be the central heating drain pipe?
It worked properly when the system was drained down for downstairs repiping and the Scottish Gas engineers couldn't see of feel
any drips there.

For the amount of water the system is losing if the leak was upstairs we'd have seen it on the ceilings by now.

I have now called Scottish Gas back to perform another isolation test and\or a full service of the boiler.

Please advise! I'm at the end of my tether and this is keeping us out of our house! We can't get new carpets and our furniture delivered until this is sorted out and the heating engineers and builders are gone.

 

[nickso]

you have water dripping from the boiler. wait until this is investigated.

 

[mlynn1974]

Hi,

Scottish Gas visit 7: 24/1/2011
It turns out the drip on the boiler is from the cold water side which "they will fix later and is not related to this issue".

They drained the system down and cut and replaced the central heating drain pipe which goes through the wall to the outside with a bit of Hep2O. The PRV was checked again and is not passing water and the expansion vessel was OK (1 bar).

The 3 foot drain pipe section was going a bit green with minor scrapes on it and a kink where it went under a joist. It didn't look badly damaged. They repressurised the system and bled radiators.

e.g. Monday 5pm
repressurised to 1.2 bar (cold), raised to 1.7 bar (hot), system running, all radiators all warm after 7 mins
8pm: 1.6 bar
11:05pm: 1.45 bar cooling down (system goes off at 11pm)

Tuesday 8:30am
8.30am 0.8 bar cold (off all night for 9.5 hours)
system left off to see what happens
7:30pm 0.65 bar cold
I topped up to 1.2 bar and ran the system till 11pm

1.2 bar initial load (cold) down to 0.65 bar (cold) in 26 hours
= 0.55 bar "loss" maybe based on 1 day running without topping up at all.

Before repiping I was losing 1 bar in 12 hours, so this is about 2 times less loss.

Wednesday 8:55am (system running for 25 mins)
1.5 bar (hot) all radiators warm without topping up
I switched the system off. I will see what it's at by 7:30pm

They've booked another appointment on Friday. I don't know if they will suggest draining the system down, cutting and capping upstairs to see if there is still a leak downstairs or upstairs or if the system is OK.

I will put it on it's normal program: 6.30am-8.30am, 4pm-11pm to give it a try today and tomorrow before they arrive. I will then see what the system pressure is on Friday morning. Maybe another isolation pressure test would be better before cutting and capping?

 

[mlynn1974]

Scottish Gas visit 8 (28/1/2011)
I was advised to keep the system switched off as topping up will be diluting the protector\inhibitor. They can only come back on Wednesday. It was too cold to keep the heating off so on Saturday afternoon I set the timer to be running twice a day until Wednesday when they can drain down, cut and cap upstairs and see if the leak is upstairs or downstairs.

Summary of leak fixes:
1. Cause: Downstairs drip leak
Loss: 1 bar per day
Fix: Repipe downstairs in copper

2. Cause: Downstairs drain pipe starting to deteriorate
Loss: 0.6 bar loss per day
Fix: Repipe CH drain pipe in Hep2O to outside

3. Remaining leak is causing about 0.4 bar loss per day.
Not found yet.

Weird observation:
On Saturday morning even though the heating was off, the central heating demand light was on. The service manual says this could be a board malfunction or the board is wet (!). I will need to tell the engineer about this. I think the tiny cold water leak on the boiler should be fixed first but the engineer said it wouldn't cause the pressure loss we are seeing and isn't a big problem.

More accurate measurements:
Saturday 4:30pm: top up to 1.2 bar cold
Monday 7:30pm: 0.5 bar cold
0.7 bar loss in 51 hours = 0.33 bar loss per day
The system runs twice (7:30am-9:30am and 7:30pm-11pm).

On another note:
Does anyone know of a telemetry system for central heating? It's really hard to find leaks especially on a ground floor.

 

[mlynn1974]

Scottish Gas visit 9 (2/2/2011)
Downstairs cut and capped.

Same leak pattern observed. This is good because it rules out the upstairs and the pipe chase.

0.4 bar per day loss running 8:30am-9:30am and 7:30pm-11pm.
e.g. 1.1 at 11pm, 0.7 by 8:30am

The pressure held at 0.7 bar for 2 days when the system was off and cold.
The central heating system was switched off on Sunday night at 0.4 bar. The pressure held at 0.4 for 5 days when the system was off and cold.

Scottish Gas visit 10 (11/2/2011)

He checked:
Primary heat exchanger (all ok),
Auto air vent (water would have been running down the side of the boiler if that was the source of the leak),
Flow\return pipes directly under the boiler under a bit of flooring (all ok),
He put a standard brass drain cock on the end of the CH drain pipe instead of a flowflex isolating valve (he didn't have one in his van the last time).

The problem sounds like a leaky joint which only leaks when system has been hot and is cooling down. I will call in the company that did the repiping downstairs and get them to check their work again.

I am glad that the pipe chase has been ruled out but wonder how long it will take them to find and fix this leak.

 

[mlynn1974]

We thought that the bathroom radiator needed repiped but it was inspected by an experienced plumber that works for the repiping company.

He checked the fittings, solum and lagging for signs of leaks - nothing.
He checked around every radiator for leaks - nothing.
He tightened a lockshield on the hall radiator. He got a good turn on one of them.
He looked at all the fittings that were exposed in the utility room - nothing.
He listened to the pipes on the kitchen radiator - hey presto! He lifted the floor board and found a leak on a new fitting in the kitchen. He ran the boiler at max temperature, not high pressure hoping to see it quicker.

The leak was more than 1 every 15 mins as thought. It was dripping. You could actually see the steam.

He removed the old fitting, replaced the copper pipe and soldered on a new fitting. He repressurised the system, bled all the radiators, waited until air had been expelled.

The system was repressurised to 1.5 bar (cold), 2 bar (hot).
Programme set to twice: 7:30am-9:30am and 7:30-11pm

We'll monitor it over the next couple of days and see how it goes.

 

[plumber1722]

let someone speak pleeeeeeeeese

 

[bengasman]

Certainly no lack of information, but what exactly is your question?

 

[mlynn1974]

I guess my question was:
Is there an easy way to detect central heating leaks without lifting all the floorboards?

The answer for me was: get a good old fashioned plumber. Run the heating at high temperature, not high pressure and listen to the pipes. If we had got him sooner we wouldn't have had to lift a bunch of tiles in the bathroom and would have saved retiling costs.

 

[BSE]

I guess my question was:
Is there an easy way to detect central heating leaks without lifting all the floorboards?

The answer for me was: get a good old fashioned plumber. Run the heating at high temperature, not high pressure and listen to the pipes. If we had got him sooner we wouldn't have had to lift a bunch of tiles in the bathroom and would have saved retiling costs.

Pressure loss within modern closed systems equates to fluid loss and invariable noticeable. Now this leak might consist of a half to a litre of fluid a day and wouldn't go unnoticed in most locations, unless it occurs beneath the ground floor but frankly finding it isn't rocket science. In my 40-years in the industry as both an installer and degree qualified building services engineer the lack of expertise of those paid as so called plumbers/service engineers never fails to surprise me.

While this is far too late to help it may assist others and the answer is yes and no.

The only way is to narrow the search down and you begin with the easy bit and check the (condensing) boiler. A visual check will determine if there's any leak to connections etc, though removing the case will help but most superficial leaks will be evident, certainly ones of this magnitude, though some may say you may have several contributing this is unrealistic.

However there are a couple of things you need to be aware of;

1 The boiler main heat-exchanger (HE) may have failed (you wouldn't know).
2 The pressure release valve may be intermittently passing

Turning the system completely off (so no condensate is produced), pressurise the system and isolate the heating circuit. Place the boiler flexible condensate pipe into a bucket and if discharge continue's and the pressure drops this will indicate if the HE has failed (not unusual and I suspect what's occurring here), any internal leak would have discharged to drain and the only indicator would have been the loss in pressure which could have occurred anywhere on the system had it not been isolated. But the continuing flow from the condensate pipe when the boiler's turned off is the indicator.

Also the PRV may pass fluid, placing a plastic bag to catch any egress will indicate if this is happening (unusual).

If a visual inspection of the boiler and the above are ok then one can usually assume any pipework in intermediate floor spaces is fine as the loss of over a litre over a couple of days would have indicators such as damp patches on ceilings however, a methodical approach is desirable and if a visual inspection fails to get results then pressure testing parts of the circuit (i.e. isolating say the GF section installing a pair of isolating valves then pressure testing that section to eliminate it.

If you though can't see the pipework you can still test and all you need is once drained cut in some strategically placed isolating valves and a pressure gauge kit (£25) that can be fitted where a radiator plug has been removed on the section being tested.

In my daughters case, her Greenstar boiler has a failed HE casting and I suspect there's more of them about, there is I understand a 10-year warranty on those. Am checking to see if this one qualifies.

 

[Dan Robinson]

Nice bit of random thread revival