Faulty expansion vessel on W'ster 24i junior

[kokoshka]

I've been told by a plumber that the reason my pressure keeps dropping (I have to top up 3-4 times a day, is due to a leaky expansion vessel. I've pumped air in, but pressure drops again. I've looked for spare part on web, but can't find exact number from handbook...8716 105 545 0, but I was told that I could fit a third party vessel anywhere along the CH system. Is this true, is it difficult, does it have to be on flow or return, would I have to be precise in charging the vessel? If I could do it, are there any brands I should avoid, or look out for? Thanks.

 

[possum_jenkins]

when you open the valve on the vessel do u get water out? if not much more likely prv is problem. This is assuming that there is a water coming gout he discharge pipework!

 

[kokoshka]

When I took the cap off the charging point (where the pump is attached), it was a little wet, but not really leaking. It only took a few strokes with the pump to get pressure up to 1.5, where it stayed for a couple of hours before dropping again. Is the PRV a difficult job? When I refer to 'pump' above, I mean bicycle pump, to top up air pressure.

 

[possum_jenkins]

you mean when you were pumping up the expansion vessel the pressure gauge on the boiler was moving yes? if this is the case then it is the expansion vessel thats knackered.

 

[kokoshka]

Yes, the gauge dropped down to almost zero. I attached bicycle pump, and as I pumped, the gauge reading climbed. I quickly got it up to around 1.5, disconnected the pump, and waited. The gauge was steady for around half an hour, then, after the timer turned the boiler on, climbed to around 2, then gradually lost pressure over a couple of hours, at which point the warning light flashed and we topped up the water pressure to get some HW and CH. 2 or 3 hours later, the pressure had dropped again. This is the pattern, and it's gradually worsening. There is a very minor and curiously intermittent leak at the pump coupling, otherwise the system appears intact. This leak, when it occurs, wouldn't fill an egg cup in a day, so I don't think it's relevant. If the fault is with the vessel, what's the best remedy, in terms of economy and simplicity?

 

[Terrywookfit]

I would suggest that you read FAQ on this subject!

It sounds as though you are not letting pressure escape whilst recharging!!

 

[Agile]

Yes, the gauge dropped down to almost zero. I attached bicycle pump, and as I pumped, the gauge reading climbed. I quickly got it up to around 1.5, disconnected the pump, and waited. The gauge was steady for around half an hour, then, after the timer turned the boiler on, climbed to around 2,

You clearly have not recharged it in accordance with the FAQ instructions.

However, if when pressurised you press the air valve pin ( as stated in FAQ ) and let all the air out then does water come out ??? If so then its failed!

An external EXV can be fitted anywhere on the system but is better on teh return and better fed by a short distance of 22 mm tube ( as you MUST do on solar!!! )

Screwfix have some listed now but I have not looked at them yet!

Tony

 

[kokoshka]

Thanks...I found the relevant section on the FAQ page. I'll do a proper check at the weekend, meanwhile I will check the EV valve to see what comes out, and post my findings. Thinking ahead, and having browsed the internet, I note that some external EV's claim to be potable, whereas others don't. Does this imply that some aren't safe in this respect?

 

[Gasguru]

Potable expansion vessels have a membrane suitable for hot/cold drinking water ie not for heating. If you do need to replace the vessel and you don't want to plumb in additional external vessel changing the internal vessel is easy on the Junior. Provided the flue has a little movement the boiler hangs on a wall jig...corgi needed for gas connection though.

 

[Corgigrouch]

If the boiler is less than 2 years old, then it is still under warranty and worcester will do the job FOC, even if it is a little over if you talk nicely to them, then sometimes they will still do it as a warranty job but a bit of charm works wonders

 

[kokoshka]

Three replies. 1, to Agile. I did as you suggested, vented the valve on the EV when the boiler was under pressure. Air escaped for about 10 seconds, then there was a very slight gurgle, and my finger was slightly wet. So, a minute amount of water, no more than a few drops came out. Since this is the case, if I charged up the EV properly, as in the FAQ section, would I be able to stagger on for a while? 2 for Gasguru, the spare part for identical replacement would cost about £60, and if I need to use a corgi installer, it would cost about £50-100 at least to do the work. If I buy an external EV for around £20 and do the job myself, then I'll be a lot happier. I'm really broke! Also, if this boiler continues to fail (a leak and something needing replacement whilst still under warranty, a new motherboard last year, and now this...and it's still only 4 years old), then I don't want to throw much more money at it. 3, for Corgigrouch, as you'll see above, the boiler is 4 years old, on it's last legs already, a true turkey. Worcester have been helpful in the past, it may well be worth pricking their conscience, I'll give it a go! Thanks one and all.

 

[Gasguru]

Are you really sure the vessel has failed....a small amount of moisture is normal. Just inflate the vessel whilst keeping the system pressure at zero. AFAIR these vessels are not the usual CIMM/ZILMET carp quality. If it has indeed failed then it is more than likely due to lack of maintenance ie it doesn't get a little air pumped into it each year. Eventually the vessel is so flat the diaphragm can become perforated as it wears against the seam.

These boilers are going through circuit boards by now but providing your local water conditions are not scaling up the heat exchanger it will still cost less to run than a new boiler. Unless you choose very very wisely many new boilers are a disaster and some require extensive servicing each year out-weighing any gas savings.....and if you're skint this is the last thing you should be doing.

 

[kokoshka]

I did this : Turned off boiler when pressure had dropped to zero, opened drain cock, allowed about 10 litres to drain off, attached bicycle pump to EV, pumped away for about half an hour, the gauge didn't move. A little air went into the EV, as I established by pressing in the valve pin, but not much. It felt as though no air was going into EV, as though air was forcing itself out probably around pump washer. Any ideas?...Half an hour later, I turned mains back on, re-pessurised to 1.5, and once boiler fired up, pressure shot up to an unprecedented 3.6!

 

[Gasguru]

If it doesn't hold any pressure the vessel has a hole in it or diaphragms leaking air out at the seam.

 

[kokoshka]

So, it looks as though I've to fit an external EV. Toolstation do one made by Watts, in two versions, a blue painted potable one which is only 5 litre, and an orange painted one which comes in sizes from 8-24 litre. The bladder in the orange one is WRC approved. It's the potable distinction between the two that worries me, are they both safe to use? Most EV's that I've seen on the web don't make any reference to this. Also, how would I fit a 22mm tee onto the return? If I could use the 15mm pipe, I could manage with a self-cutting tap, but as far as I'm aware, there isn't a 22mm tap available. I prefer to use plastic fittings, in fact, I have no experience with copper.