Losing Pressure Every day

[Danny P]

I have a Potterton puma 80 combi boiler and for the last few weeks it has been losing pressure every day. Each morning when the heating is set to come on the system doesnt fire. When i check the boiler the low pressure light is on and i have to top up the system with the filler.

From these pages it says i may have a faulty (dirty) Pressure relief valve, it takes about 5 or six hours for the pressure to drop is this likely to be the fault?

Any help would be appreciated.

 

[sterose]

It could be a leak, but check out this other thread first.

//www.diynot.com/forums/viewtopic.php?t=4635

 

[oilman]

If you have a leaking PRV, you should see water dripping from the discharge pipe. If not the leak is somewhere else.

 

[Danny P]

Yes i have noticed the pressure rise when the system is on, maybe i've been putting to much water back in. it goes into the red, when getting up in the morning the pressure is in the low.

Do i have to fill the pressure back to the indicator line exactly? i think its about 2 bar? if i filled it to much would the relief valve kick in when cooling>

 

[oilman]

Search the forum for "expansion vessel" and "filling loop" theres plenty of posts about setting the air pressure and the system pressure.

 

[Danny P]

As i have read throught the forum i remembered we had water mains problems a few weeks ago due to new houses been built the neighboughs dont have a combi and lost water mains pressure, we then had dirt in the water, could this have caused the PRV to malfunction?

If it is the PRV where abouts is it situated? And is it easy to remove, i have a Potterton puma 80?

Any help would be appreciated

 

[ChrisR]

As indicated by oilman, this is a faq. You need to pressurise your expansion vessel. What is happening now is that the water has nowhere to go when it expands on heating so it leaves via the Pressure Relief Valve. Then there's too little water in the system when cold.

Let water out of the sytem via the PRV (red knob), then pump up the Expansion Vessel (at the back) with a car footpump (easy by hand) to about 12psi. If water comes out of the EV valve you'll need to get it seen to - come back.

Keep an eye on the PRV's pipe afterwards- they are inclined to keep leaking in which case you'll need a new one.

 

[Danny P]

Phoned for a plumber he says the expansion vessel may be faulty but it isnt worth refilling by foot pump as it will only last a couple of weeks, not being hydrogen?

Put a glass under the PRV outlet and sealed with cling film got up in the morning to find about 5mm of water, he says with it being a potterton 80 the unit will have to come off the wall and a new expansion vessel fitted, this isnt worth doing you may as well go for a new boiler after the labour (4.5 hours?).

Could you advise?

Would you recomend a new boiler if so what kind without being too pricey.

Thanks for all the help by the way, first time buyer with faulty boiler, should have seen that one coming.

Got to keep smiling though it's only a boiler

 

[oilman]

.....may as well go for a new boiler.......

Yes I know the problem, I had the same type of thing with a car once, ashtrays got full,... needed a new car........not!!!

Phoned for a plumber he says the expansion vessel may be faulty but it isnt worth refilling by foot pump as it will only last a couple of weeks, not being hydrogen?

I hope he meant nitrogen. The problem is that oxygen (21% of air) gets through the membrane in the expansion vessel, so the pressure will drop a bit in a couple of weeks, and you may need to pump it up again, but then it will have only 21% of that 21% oxygen to leak away. Exactly the same thing happens with car tyres!!! So afriad he's not quit correct here. As you saw from the other posts, the vessel's pressure should be checked annually and replenished and none of us have a nitrogen bottle.

.... he says with it being a potterton 80 the unit will have to come off the wall and a new expansion vessel fitted, this isnt worth doing you may as well go for a new boiler after the labour (4.5 hours?).

I'm now very suspicious, this will probably cost a few hundred more than fitting a new expansion vessel, to pay for the boiler. Get another opinion, even British Gas's opinion might be handy.

You could have an external expansion vessel, and never mind the one on the back of the boiler, your problem is probably space to fit it in. But you may not need one if the tests are ok.

Would you recomend a new boiler......

Not unless you really need one, or you are rich.

 

[ChrisR]

Agreed. Get an honest plumber.

 

[Danny P]

2nd plumber organised, hope its just a pump job, thanks guy's.

 

[james2210]

What was the outcome on this one as I think that I'm in a very similar position. We've just bought a house and the pressure drops every day and the system has to be refilled.

 

[oilman]

And have you done the checks suggested?

 

[james2210]

I've pressurised until the low pressure light goes off (gauge is reading just under 1bar) and then run the heating and watched as the pressure gauge goes to 3bar+. At this point, excess water is send through the PRV and I can see it dripping from the overflow. Then when the system cools, the pressure is too low for the boiler to re-ignite (under ½bar). The expansion tank on the Puma 80 is situatued right behind the boiler and looks like you need to take the boiler off the wall to get to it. I've had a good look round but cannot find a valve to check the expansion tank pressure or to see if it contains water. The expansion tank connects into the same manifold as the PRV and I've seen another post from someone who said that the hose was clogged. If I depressurise the system and remove the hose to check for gunk, will I need to repressurise the expansion tank afterwards? Also, what can I expect when I unscrew the expansion tank hose from the manifold, would water spray everywhere?

All help is greatly appreciated. If anyone knows the whereabouts of the expansion tank pressure connector I'd love to know.

 

[ChrisR]

I'm pretty sure it's at the top.