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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Baxi 105e Expansion Vessel https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1291975720 Message started by Paul Woodward on Dec 10^th, 2010, 10:08am

Title: Baxi 105e Expansion Vessel
Post by Paul Woodward on Dec 10^th, 2010, 10:08am

Hi Guys,

Been having problems with my boiler losing pressure for the past week. I have determined it is probably my expansion vessel.

Would the following be a good way to determine if I have a faulty expansion vessel:

1. Power down Boiler
2. Isolate Heating Flow and Return
3. Drain boiler via pressure relief valve
4. Check pressure on Expansion Vessel
5. Pump pressure to 0.75 bar if required
6. leave system off for several hours
7. Check pressure has held

I am assuming that if the pressure has dropped then the unit is faulty and I can arrange for a plumber to fit a remote vessel on the return pipework.

Any advice before I go ahead on perform this task over the weekend would be appreciated.

Many Thanks

Title: Re: Baxi 105e Expansion Vessel
Post by thescruff on Dec 10^th, 2010, 8:31pm

If you quickly depress the valve on the expansion vessel you should get air, but if water then it's duff.

Do not drain the boiler with the pressure relief valve as they rarely re-seal again and you'll be changing that as well.

Are you loosing water through the PRV at the moment.

Title: Re: Baxi 105e Expansion Vessel
Post by Paul Woodward on Dec 12^th, 2010, 9:53pm

Hi Scruff,

I have always had a drip on the PRV since the day I moved in about 3 years ago which I assumed was because it had activated and never resealed which I have heard is a common problem.

I've run some tests over the weekend and I have identified two separate leaks on the boiler. One on the Heating Flow near the isolation valve so I am going to order a replacement valve and the other is on the connection to the pump.

I am not sure what to do about the pump leak but I am guessing there is some sort of gasket I can replace without having to replace the pump unit.

Would I be correct in thinking that if water can leak out of the two spots mentioned above then so could pressure from the Expansion Vessel?

I perform the procedure I mentioned in my previous post and I lost 0.4 bar of pressure (with no water in the boiler) in the space of about 10 hours.

I will take your advice into consideration next time and use the dedicated drain valve on the boiler.

With 2bar of water in the system and the F&R isolated I lost 0.75bar of pressure in 3.5 hours.

All tests were performed with the boiler powered down.

Forgot to mention I have never had water come out of the schrader valve when testing / re-inflating.

Title: Re: Baxi 105e Expansion Vessel
Post by thescruff on Dec 13^th, 2010, 1:44am

1st if the PRV is dripping it will need to be changed if you can't stop it by turning the knob a few times.

The other leaks on the boiler need to be cured as you say.

If the pressure is dropping with the boiler valves shut, although if the boiler is loosing water I can't see how you can test, then you also have a leak in the system, check all the radiator valves and nuts first.

If there's no water in the expansion vessel then you just need to top the pressure up to 0.75-1bar depending on the size of the system.

Quote:

Would I be correct in thinking that if water can leak out of the two spots mentioned above then so could pressure from the Expansion Vessel?

No the air in the expansion vessel is sealed from the system, unless the vessel is duff. (water when you press the little valve)

Title: Re: Baxi 105e Expansion Vessel
Post by Paul Woodward on Dec 13^th, 2010, 11:26pm

Cheers Scruff,

I am going to try and get the leaks sorted but it sounds like my expansion vessel is duff too then because after topping up to 0.9 bar it dropped to 0.5 bar in about 10 hours.

I had the boiler drained and switched off all day.

I really appreciate your help.

[smiley=thumbsup.gif]

Title: Re: Baxi 105e Expansion Vessel
Post by greg on Dec 16^th, 2010, 7:36pm

test the EV schraeder valve with some soapy water to see if its leaking