Megaflo won’t stop dripping

[Exfarmer]

I know nothing of the workings of these systems, we have one installed and it has recently started dripping from the overflow / relief valve thingamy
the instructions say to shut off mains open bottom hot tap and relief valve until empty then recharge system.
done this but still dripping
it has happened before but always stopped in the past
Any ideas? If you have has anyone tried claiming on the 25 year warranty it is now about year 17

 

[Boydvalley]

Relief valve leaking. Maybe bits of calcium if you’re in hard water stopping it from seating/ build up of calcium from dripping. Simple to fit a new one. Got one about the same age. Should recharge every 6 months. I never remember either.

 

[Exfarmer]

Relief valve leaking. Maybe bits of calcium if you’re in hard water stopping it from seating/ build up of calcium from dripping. Simple to fit a new one. Got one about the same age. Should recharge every 6 months. I never remember either.

many thanks, I suspect you are right I will try and find a plumber to replace the valve. Sadly the original installer never got paid as the builder went bust, so he is not inclined to help at all

 

[f0ster]

if it has an expansion vessel fitted check that it has not lost all of its air,

 

[Nukemall]

Has your incoming mains pressure increased? Had the prv on the tank replaced, but had to put a seperate prv on our incoming mains supply to stop ours dripping.

 

[Exfarmer]

Has your incoming mains pressure increased? Had the prv on the tank replaced, but had to put a seperate prv on our incoming mains supply to stop ours dripping.

Do have pressure regulator on the system, water softener specified it

 

[Lakesdigger]

Often find relief valves don't seat properly and leak once they get older and so when you follow the recharge process they then drip and need changed.
Megaflows rely on an air gap in the top of the cylinder rather than an expansion vessel but if I'm not mistaken it's debatable whether it works well enough and have seen expansion vessel added to the system.

 

[Exfarmer]

Often find relief valves don't seat properly and leak once they get older and so when you follow the recharge process they then drip and need changed.
Megaflows rely on an air gap in the top of the cylinder rather than an expansion vessel but if I'm not mistaken it's debatable whether it works well enough and have seen expansion vessel added to the system.

We have expansion vessel as well

 

[Steevo]

@Adeptandy is the oracle for such things.

 

[Adeptandy]

@Adeptandy is the oracle for such things.

Not sure about that, but usual job is to replace the air bubble in the top. The sequence is in the manual for the cylinder

 

[Exfarmer]

Not sure about that, but usual job is to replace the air bubble in the top. The sequence is in the manual for the cylinder

Done that, made no odds

 

[Adeptandy]

Is it dripping through the tundish ?
If so it’s most likely the Temperature and Pressure Relief Valve passing

 

[Exfarmer]

Is it dripping through the tundish ?
If so it’s most likely the Temperature and Pressure Relief Valve passing

Is the Tundish the little open cone shaped device? In which case yes, it sounds like i need to replace one of those two valves. I have tried opening and closing them repeatedly to see if it solves the problem, but no joy there, hopefully I can find a nearby plumber

 

[Steevo]

Is the Tundish the little open cone shaped device? In which case yes, it sounds like i need to replace one of those two valves. I have tried opening and closing them repeatedly to see if it solves the problem, but no joy there, hopefully I can find a nearby plumber

Are you sure you're looking at the right valves?

Relief valves aren't there for the user to open/close because they rely on excess temp or pressure for that to happen.

 

[Adeptandy]

Is the Tundish the little open cone shaped device? In which case yes, it sounds like i need to replace one of those two valves. I have tried opening and closing them repeatedly to see if it solves the problem, but no joy there, hopefully I can find a nearby plumber

yes, that’s the tundish
Some have a PRV and T & PRV separate, normally rated at 6bar, but the seen the odd one up to 8 bar

 

[Adeptandy]

It’s a simple job once the water’s drained a bit

 

[Adeptandy]

Are you sure you're looking at the right valves?

Relief valves aren't there for the user to open/close because they rely on excess temp or pressure for that to happen.

Yes, both valves can be opened manually, it does generally make the drip worse and often results in a trickle 🫣

 

[Adeptandy]

T & PRV will be something like that.
Up near the top of the cylinder

 

[Exfarmer]

Many thanks for all the help. Plumber just been and diagnosed both valves need replacing which I agree with. Hopes to be back later in the week

 

[Boydvalley]

A bit of explanation for those who don’t know.
A mega flow is different to other hot water tanks in that the expansion is an air bubble inside the the tank.
The air bubble needs recharging every six months by allowing air in through the pressure Relief valve by opening hot taps to drain water while the mains supply is turned off. Hence why the pressure relief valve is manually opened.

The central heating circuit still needs an expansion vessel which is why @Exfarmer says he has both.