Boiler losing Pressure

Newark17

I have a Worcester Bosch Greenstar 30si Boiler, and it keeps losing pressure and needing toping up with water. We have had an engineer out and he drained the system (half a bucket or so) and he pumped up the expansion vessel (using a special tool)  

while he was here, we bled one of the radiators. 

Initially there was water going coming out of the discharge pipe but that does not happen now when I top the system up to 1and a Half on the pressure meter. I have put a plastic bag under the discharge pipe to check for any overflow. 

 But the pressure keeps dropping and requiring topping up,(now more frequently – after just a few hours) I have put newspaper under the boiler and there doesn't seem to be any water leaking from it, and we have checked all the radiators and towel rails, and we cannot find any leaks or wet patches anywhere. We cannot see any wet patches anywhere in the house (or ceiling).  

The engineer is currently on holiday for another week. 

We are at a loss to know where the water is going. 

WIAWSNB

Hi Newark.

The leak is either coming from within the boiler, or without. The boiler can be isolated from the rest of the system - rads, etc - quite easily, and that would be a sensible first check, I think (since you have discounted it being the discharge valve).

So, could you take a nice clear pic of where the pipes enter the boiler on its underside, please - say at a 45o-ish angle looking up, showing all the pipes and connections.

Ta.

Newark17

pic attached (newspaper is where i once saw water when it was pouring with rain- but there is a leak in the roof ) and no sign of any dampness now

P1040279.JPG

WIAWSNB

Yikes, What's caused all that corrosion?

Anyhoo, you need to ID the boiler flow and return pipes. They are, I'm pretty sure, the first copper pipe on the LH side beside the white plastic pipe - the flow - and the similar pipe on the RH side (with a thinner? Copper pipe on the very end, I presume the discharge pipe.)

These pipes have valves on them, operated via a screwdriver slot or small spanner. If you close off these two valves, then you've isolated the boiler from the rest of your system. If the pressure still falls, then the loss must be from within your boiler. If the pressure remains steady, but then drops the moment you reopen a valve, then the loss is from the rest of your plumbing - rads, pipes, whatevs.

So, allow the boiler to be cool - a good time is before bed, or if you are out for the day. Power it down fully - mains switch off. Pressurised your boiler until you have a eady-to-note reading - take a photo of the gauge. Then close both valves through 90o, and leave it for as long as possible.

After a few hours, check the reading. Has it dropped? Open one valve whilst keeping a steady eye on the gauge - does it budge? If so, which way?

Newark17

Hi WIAWSNB

Thanks for your comments

The corrosion was caused by Trident Housing who who put a lean to on their property next door which flowed directly onto the rear wall of the outbuilding the boiler is in. The resulting damp caused the ruination of all the cabinets in the room and causing the ceiling to partially collapse before they finaly removed it (after I took out legal proceedings against them).

However back to today - I got hold of the engineer and he came out - he opened up the heat exchanger and it was full of clumps of a wet black ash like substance. He has cleared all that out and marked the pressure valve reading and isolated the boiler over night.(Its going to be a cold Night! ) He spoke to another engineer who is a Bosch specialist and he thinks it could well be the heat exchanger has failed. A new one is around £600 pounds which is not worth it on a 15 year old boiler, but I see you can get guaranteed refurbished for around £100 so I do not know what to do.

WIAWSNB

The mainX is a big part to replace, so get an all-in price.

I suspect, at 15 years old, it may be time to replace :-(

Newark17

The engineer came back today - the needle on the pressure gauge had not moved at all - there is no water leaked anywhere in the boiler. He turned the valves back on and the pressure on the gauge did not change, either way. (He was very suprised by this). I have waited a further 2 hours and their is still no change on the pressure.

So I am not sure what the problem can be

Just checked again, Another 2 Half hours later - pressure now down to zero!!!

No water in the Boiler or the overflow

Engineer has spken to a collegue who deals with mainly Worcester boilers and he says it is very unusual, I have pressured up to 1.5 bar. He has asked me to bleed all radiators (14 + 2 towel rails so it will take some time) and keep an eye on the plastic bag on the overflow.

WIAWSNB

https://forums.moneysavingexpert.com/discussion/comment/81898950#Comment_81898950

Annoying!

It may be a leak that requires the boiler to be hot - that isn't unheard of. Eg, a hairline crack in the mainX which only opens when the boiler is running.

Is it a combi? If so, then I understand it can be run in just DHW mode, so that means you can isolate the flow and return again, turn the CH demand fully off, run a hot tap for a few minutes (throw someone in the shower...), and monitor the pressure throughout.

If the pressure climbs towards 2.5 bar at any point, best to shut it down.

But, monitor starting cold pressure, and compare this with afterwards after it's cooled down again, and also keep that bag over the discharge pipe.

Note the figures, and again as you reopen the valves.

If no change, I'm stumped, tho' is still leaves the option of the EV leaking air again, and this could cause a pressure drop.

Newark17

So I am not sure what the problem can be

Just checked again, Another 2 Half hours later - pressure now down to zero!!!

No water in the Boiler or the overflow

Engineer has spoken to a collegue who deals with mainly Worcester boilers and he says it is very unusual, I have pressured up to 1.5 bar. He has asked me to bleed all radiators (14 + 2 towel rails so it will take some time) and keep an eye on the plastic bag on the overflow.

Have now bled all radiators and no air in any at all and no sign of leaks.

The pressure does only seem to drop when the heating is on

It is a Combi Boiler

 If there is a hairline crack in the mainX which only opens when the boiler is running would this show water deposits in the boiler - as there is no sign at all Where does the water go?.

Is there any way you can detect a hairline crack in the mainX

WIAWSNB

https://forums.moneysavingexpert.com/discussion/comment/81899824#Comment_81899824

The water from an internal mainX leak would end up coming out the plastic condensate pipe.

That is trickier to detect, since condensate will be coming out as normal when the boiler is running.

You could place a bag over that pipe end too, but you'd need to make it a decent size bag that won't fill in normal use! A carry-bag size in clear plastic would be ideal, and you can monitor it and empty when required.

Once the boiler is off and has cooled down, condensate should stop coming out, so any significant liquid in there would be suspicious. If your system water has 'inhibitor' in it - as it should - it'll have a distinctive chemical smell. Condensate on its own is largely non-smelly, but might have a light 'burnt' odour.

If you bleed a rad again, catch a teaspoon's worth, and give it a good sniff. Compare that with what comes out the condie pipe - any of the same whiff present?

Silly Q - do you have litmus paper or baking soda? (Not baking 'powder')?! Condensate is acidic.

The pros will have other methods, such as adding an indicator to the system water that can then be detected if it comes out. I've heard of folk DIYing this using a small quant of smelly 'essential oils'!

Newark17

Thanks I will pass thi on to my engineer