Vaillant ecoTEC Plus 831 R1 - Pressure Vessel

[Smithy723]

I have a Vaillant ecoTEC PLUS 831 R1 boiler. Over the summer we have not had any issues, only having to recharge the pressure once in 6 months.

We recently turned on our central heating and the boiler is now suffering from a total loss of pressure on a daily basis. I checked the pressure release pipe outside and found it to be dripping.

We called in a plumber who diagnosed a faulty pressure vessel diaphragm and suggested replacing the unit. I did a bit of research and found a replacement part (P/N 181051) available for £59 (much cheaper than the £120 he wanted).

I am going to order the replacement vessel but am not confident about replacing it myself. Does anyone know if it is the kind of job an amatuer can do? If so, how would I go about doing it?

I am also concerned, after doing a bit of research, that the pressure release valve may have been damaged by the faulty vessel, is this the case?

Any help would be greatly appreciated!

Thanks

 

[twgas]

Before you order a vessel check the pressure in the one you have. The faqs explain.

 

[Smithy723]

Before you order a vessel check the pressure in the one you have. The faqs explain.

Thanks Mick, I have tested the pressure as per the FAQs and very little air came out! No water came out either (which I take it is a good thing)

I want to follow the rest of the instructions to repressurise the PV but not sure where the drain cock is. Any suggestions?

Thanks

 

[Smithy723]

Hi, I followed the instructions to repressurise the PV as per the FAQs and everything went as expected, removing a considerable amount of water. When finished I filled the boiler water back up to the centre of the gauge (there are no values on the gauge, only coloured section indicators).

When I turned the boiler back on and the water heated up, the water pressure slowly went from the centre of the gauge to the max. Should this happen? I thought the PV stopped this happening by increasing the pressure of the air, not the water!

Any thoughts? Assistance is much appreciated, already had one cowboy trying to rip me off by telling we the PV needed replacing when, from what I can tell, it's perfectly ok!

Thanks

 

[Phill Peck]

You will probably find he is not a cowboy, but trying to do a professional job.

IMO re pressurising an expansion vessel is a temporary repair
the £120 he quoted you for the part is the retail price
bearing in mind he has to collect that part and guarantee it for 12 months. Yes parts are available online, but they are not always the genuine part and you will have to wait for it to be delivered and also pay delivery

Yes I would replace the prv aswell.

In this situation I recharge the vessel and charge my call out fee. Aswell as advising and quoting for the replacement

 

[Smithy723]

Thanks, fair point about the cost of the part!

Why is it only a temporary fix? If the diaphragm inside the PV is not damaged surely it should work as normal.

Still not sure if the water pressure should be changing as much as it is, is this normal?

 

[Phill Peck]

The diaphragm can be over stretched so even if you pump it up again it will fail again (not defiantly but can do)
also they can have a small hole/tear or become disconnected at the edge only when under pressure. So it can appear to hold pressure but as the pressure rises in the system it causes it to fail again.
I have re pressurised vessels many time over and over

If you have your boiler serviced every year the vessel should be checked.
If the pressure on the air side is allowed to get too low then the diaphragm can be over stretched when the system gets hot.