Boiler constantly losing pressure.

Discussion in 'Engineers' Talk' started by Dougie1702, Mar 9, 2018.

  1. Dougie1702

    Dougie1702 New Member

    Woke up this morning and pressure was absolutely dead zero. This means it's the boiler yeah? So I can tell the gas engineer thats coming out to fit a new pump etc, that I have done this test and it will hopefully direct his attention to the boiler and not pulling up my floorboards?
     
  2. Mike83

    Mike83 Active Member

    If the isolation valves were fully closed I'd be looking at the heat exchanger.
    If the water was coming from the prv pipe you would have noticed that and you've previously stated the boiler insides are dry.

    Get the gas engineer to carry out the same isolation test if he doesn't believe your conclusions.
     
  3. Dougie1702

    Dougie1702 New Member

    Boiler insides are dry yes. I noticed that with the isolation valves closed this morning, the dial wasn't just reading in the zero region, it was lower than the zero region, like it had completely emptied itself.
    I have tied a bag round the PRV overflow that is situated on the outside wall, it is bone dry.
     
  4. Mike83

    Mike83 Active Member

    The white pipe at the far right. Pull this down about an inch. This will then let us see if water is coming from the heat exchanger.
    Obviously top up the pressure and don't use the heating or hot water.
     
  5. Bob Rathbone

    Bob Rathbone Well-Known Member

    Sounds like the first line of a classic R&B riff. You appear to have covered all the bases, I'm stumped.
     
  6. Bob Rathbone

    Bob Rathbone Well-Known Member

    Is their an auto air bleed on the boiler at the top. It may be that the pressure you are losing is trapped air not water.
     
  7. Tom86

    Tom86 New Member

    Hmm. Interesting reading.

    I don't know, I was just thinking... if heat exchanger is leaking, shouldn't be there some water inside and under the boiler?

    That water must end somewhere, right?

    So I was thinking further... IMO, the only place where you don't realize any leak is your tap. Isn't it possible that diverter valve failed ( in the very strange way ) and it diverts small amount of CH water to DHW system...?
     
  8. Dougie1702

    Dougie1702 New Member

    The boiler pressure went through the roof last night. Into the red and opened the PRV. The pressure vessel was just charged though so any other reason for this?
     
  9. terrymac

    terrymac Active Member

    Tom ,if heat ex is leaking the water is evacuated with the condensate from the boiler ,so you wouldn't notice as the condensate pipework is always dripping , whilst boiler is on. Regards terry.
     
  10. terrymac

    terrymac Active Member

    Did you over pressurise the system yesterday. Or maybe not fully closed the filling loop ?
     
  11. Dougie1702

    Dougie1702 New Member

    No, it's at a normal pressure then once the heatings been on for 10 mins, it's at nearly maximum pressure (in the red)
     
  12. terrymac

    terrymac Active Member

    Check all valves that you have been working on are fully open ,except filling loop which should be fully closed. Otherwise it points to a problem with EV .
     
  13. Dougie1702

    Dougie1702 New Member

    EV? Expansion vessel? That was just charged etc with the proper air the other day... How does this fail? Split diaphragm?
     
  14. terrymac

    terrymac Active Member

    Yes ,or not done properly. Valve leaking air out maybe.
     
  15. Bob Rathbone

    Bob Rathbone Well-Known Member

    Or the secondary heat exchanger leaking?
     
  16. Dougie1702

    Dougie1702 New Member

    The boiler was always looked at by a professional.

    The boiler is now finally fixed, needed a new expansion vessel.

    Not without them leaving a gas leak when they changed a water pipe a few days earlier. They took the gas pipe off and left a leak, had SGN out and they said it was due to this leaking pipe inside the boiler. I then proceeded to complain to the company that provides my cover about this, and the manager of the company, didn't take kindly to this and started to moan about how much the repairs had cost him thus far and that I only pay 'X' a year....

    Great company... I pointed out that if they had done their job correctly in the first place it wouldn't have cost his company so much money in labour etc.

    So my next question is, can this company be reported about the gas leak to a relevant authority? I'm in Scotland btw.
     
  17. Bob Rathbone

    Bob Rathbone Well-Known Member

    I would think so as they should have tested for gas security during the commissioning stage. if it was the expansion vessel at fault, you should have seen water being discharged from the vent pipe, you did test for this. For when they return, get a hitching rail outside for them to tie up their horses.
     
  18. rogerk101

    rogerk101 Active Member

    I'm glad it's all sorted, but it's still a mystery to me how those symptoms were caused by a faulty expansion vessel. I'm guessing it's an internal EV (as in built in to the boiler), so probably around 8 litres. In a correctly balanced system, that's 4 litres of air and 4 litres of water each at somewhere around 1 bar. If the EV was faulty, the diaphragm was pierced and the water ended up flooding the entire EV, so 4 litres of water from the CH system displacing 4 litres of air. This seems reasonable when the CH system was still connected, but it doesn't seem reasonable when it was isolated, but not when it was just the water in the boiler. Where was all this water going on each subsequent repressurising every morning? I guess we'll all remain in the dark on this one, unless someone can provide an explanation that puts us out of our misery.

    Did they also happen to replace the filling loop with its double check valve? I've had both ends of a filling loop fail before, which contaminated my drinking water with CH water when the pressure in the CH system rose to be higher than my mains (which are regulated to 3 bars).
     

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