Boiler making hissing noise

[theonejat]

Just switched the central heating on in my house and my boiler made a hissing noise for around 2-4 seconds, its a Remeha Avanta Plus and I've noticed in recent weeks that its not keeping its pressure, I can refill it fine but it will then drop back down, sometimes within hours. It's due a checkup but im not covered financially for any parts that may be needed. Please note that it only hisses when central heating is turned on, not when any hot water is run.

Just wanted to know if this was a serious problem? If anyone knows what's up or could give me some help?

Many thanks in advance,

Jat.

 

[oldbuffer]

If its losing pressure, then there is a leak either within the boiler or in your heating system. If air is getting in when the water leaks out, it is likely that your hissing sound is that air being released via the automatic air valve inside the boiler casing.

I think you need to get it attended to fairly promptly. Air in the system leads to corrosion of the insides of the radiators and the resultant sludge can block the heat exchanger making for a very expensive repair.

 

[Justin Passing]

Check the Pressure Relief Discharge pipe - the one which is copper and goes out through the wall.
If you aren't sure if it's wet or not, tie a plastic bag over it.
If it's "letting by" for whatever reason, it'll tend to keep doing it.

How hight does the pressure go if you recharge it ( to 1 bar say) then put the heating on?
If it shoots up then the pressure vessel needs pumping up.

 

[theonejat]

Check the Pressure Relief Discharge pipe - the one which is copper and goes out through the wall.
If you aren't sure if it's wet or not, tie a plastic bag over it.
If it's "letting by" for whatever reason, it'll tend to keep doing it.

How hight does the pressure go if you recharge it ( to 1 bar say) then put the heating on?
If it shoots up then the pressure vessel needs pumping up.

When I have the heating on the pressure rises quite high (up to as much as two, sometimes more time dependent)

But as soon as I turn the heating off this will slowly decrease, and if I allow more pressure into the system, it will slowly decrease too.

No water coming out from the copper pipe leading outside from what I can see.

Does it sound like the pressure vessel? If so is this a costly fix if it cant be pumped and needs replacing?

 

[CombustionGuy]

First thing is it needs the vessel recharging.

 

[theonejat]

First thing is it needs the vessel recharging.

Ok thanks. I hate asking this question because obviously it can vary but is there a price I should NOT be paying for such a job? Or does it all depend on call out fee?

 

[Justin Passing]

I can't remember any particular difficulty with this boiler so a pressure vessel recharge, and replacement pressure relief valve, should be within an hour.
It's advisable to change the PRV if it's been letting water out - you should check, as described.
New PRV ?? guess £10 - £30 for the part.