low pressure and leak c/h boiler

[androot]

My question is regarding two issues one of which is already a history but may help define the problem. Couple of days ago I noticed a leak outside of the house from the pipe which I think is called drain or safety pipe. Yesterday I noticed that pressure was around 3.5 bars, and i know it should be around 1. So i looked for some advice on the net and followed it - I drained some water from the radiator and the pressure droppped. Unfortunately a while later it started rising again. So I used another tip and turned pressure release valve - it helped. After raising pressure from 0 back to where it should be (using the valve on the loop, dont know how to call it) the pressure dropped again and my wife noticed that the leak outside became serious. Is it the PRV which causing the problem or something else?
Please help.
Andy

 

[jtc21]

I'm guessing the filling loop was left open/expansion vessel flat to cause the pressure to rise and activate the safety PRV. So now you need the PRV cleaned/changed + the expansion vessel repressurising.

 

[muggles]

Your expansion vessel is probably either depressurised or more likely blown, although opening the PRV may have allowed muck to get onto the seal, making the dripping outside worse. Get an engineer in (or you can fit a new expansion vessel yourself if you're handy with the spanners)

 

[Heatfront]

sounds like your filling loop valve was letting by water thus increasing the pressure.dont leave loop conected after filling.

it is common after using pressure relief to drain system for it to leak due to muck getting stuck on the seating,try filling and releaseing water from pressure release again this may cure,check to see if water coming out of pipe outside.If it does not stop you will need to replace or clean prv valve.

 

[androot]

Thank you for all replies. One thing has to be said. The pressure is going up and down, there is no rule to it. The filling valve is fully closed. Seems like the prv is not sealed properly, when i bend it slightly it starts releasing the pressure more or less. I can do DIY so can change the valve but not sure if it really is prv.
Thank you

 

[Heatfront]

Thank you for all replies. One thing has to be said. The pressure is going up and down, there is no rule to it. The filling valve is fully closed. Seems like the prv is not sealed properly, when i bend it slightly it starts releasing the pressure more or less. I can do DIY so can change the valve but not sure if it really is prv.
Thank you

disconect filling hose altogether valve may be fully closed but it can still let by water if faulty,hose should not be connected when not filling.

 

[MANDATE]

The pressure is supposed to go up and down. Should start about 1 bar and as the water heats up and expands it compresses the 'air' (if theres any in) in the expansion vessel and pressure will rise to about 2 bar.
A fault with the vessel will make pressure rise too much and open the PRV

 

[androot]

I checked the filling valve and its not letting the water in. Seems like its something bigger requiring a serious job. My question is can i do it myself? Dont enen know if its the prv or ex vessel causing the problem.

 

[MANDATE]

Take note of the rise in pressure when you put heating on.
If your starting at 1 bar and its reaching 3 bar then the PRV will open and discharge some water.
The EX Vessel is supposed to contain 'air' and virtually no water before heating is switched on. This gives ample scope for the extra water generated from expansion to enter the vessel and compress the full volume of air. This of course increases the pressure.
Of course if the vessel has lost some of its air charge it will already have some water in it which results in less air. The less air to compress the higher the pressure rise. You just need to remove the excess water out of the vessel while charging it back to original setting about 0.8 bar.

Regarding the PRV I think it has already been mentioned, Any dirt that may have been trapped on the valve seating face may cause a slight leak.
You can secure plastic bag on the discharge pipe overnight while heating is off and pressure at lowest and see what it collects.
You can do it with heating on when the higher pressure will increase the flow.
If you can isolate the boiler by closing the flow and return valves, then open the PRV manually, you can recharge the ex vessel.
You can also re place the PRV or remove it for cleaning.
I removed one recently, managed to dismantle it after making a 'C' spanner to undo the valve head. I now know I could have dismantled it in situ if spanner was available.
Can you do it? I don't see why not

 

[androot]

Hello, again.
Thank you everybody for sparing some time to read my boring posts.
Well, I checked everything I could and the final outcome is that: case 1 - the pressure rises to about 3 or more bar and the leakage is almost unnoticeable, case 2 - the leakage is quite serious and the pressure is stable around 1.5bar. Currently the case 1 is on. What I notice as well is that the pressure drops to 0 and leakage is gone when I close the main water feed to the boiler, and funny thing happens when I open hot water tap - the pressure rises by around quarter of a bar and drops back with a squeaking sound when I close the tap. Important thing is that filling valve is 100% sealed. I'm about to remove the prv and possibly change it, but need to be sure if its really prv.

Andy

 

[MANDATE]

The way I see it is that the PRV may have dirt on its seating face and may allow a leak, the amount of leakage will be related to the pressure.
Low pressure low leakage with higher pressure the leakage will be more.
However it's not the PRV that causes the pressure to go to 3 bar.

If the pressure goes up to 3 bar without heating on, that would suggest water at mains pressure is leaking across to the heating water somewhere inside the boiler.

If the pressure goes up to 3 bar from 1 bar when the heating is put on, then that is due to a expansion vessel fault.

Initially the vessel needs to contain no water and of course being the right size to accomadate the extra water as a result of expansion.
For example pushing 4 litres of water into a 8 litre vessel would compress the air to half volume, which would double the pressure. So going from 1 bar to 2 bar is considered OK.
Now suppose there was already 2 litres of water in the vessel when the extra 4 litres goes in.
The 'air' volume gets reduced to a third, so the pressure trebles.
This is how the pressure increases from 1 bar to 3 bar.
So I think there's nothing to be gained, unless you address both problems at the same time.
There is also a possability that the diaphragm in the vessel may be ruptured and the vessel has contains no air.