Megaflo Unvented Air Gap Recharge Water Doesn't Stop

[danielson]

I have a megaflo unvented cylinder on the first floor of my property and I am trying to recharge the air gap. I have turned off the incoming cold mains valve upstream (and right next to) the pressure regulating valve and then opened the hot water taps at the lowest point in the house. The problem I am getting is that I have had the water running out of these taps for at least 10 minutes with some really loud gurgling noises from the tank while the water is running. The hot water tap flow reduced significantly and did actually stop for around 10 seconds thinking it had worked (so I can then turn the TRV valve on the side of the tank to recharge the air gap), but it suddenly started to emit more water and again didn't stop.

I did think it could be the mains supply valve right next to the PRV that is faulty but even when I turn off the whole mains water the same issue occurs. My upstairs cold is also tapped downstream of the PRV as I was thinking there could be an issue where the cold supply is flowing back around the mixer valves in the bathrooms, but since the feed is downstream of the PRV and mains shut off this shouldn't be an issue? The only other tap that could be causing the issue is the kitchen as that is fed from the mains supply, i.e. upstream of the PRV for the hot water cylinder?

 

[SJB060685]

When you turn off the water on the incoming mains to the house does the kitchen tap stop?

 

[danielson]

When you turn off the water on the incoming mains to the house does the kitchen tap stop?

If I turn off the incoming mains supply to the house then yes the kitchen tap does stop but haven't properly tried this when switching on the hot tap in the kitchen for recharging the air gap. Maybe the kitchen mixer tap is the culprit as the cloakroom doesn't have a mixer.

 

[SJB060685]

I suspect it could be as well like you. You don't have another cold main coming into the property do you?

 

[danielson]

I suspect it could be as well like you. You don't have another cold main coming into the property do you?

Good call but I am pretty sure after searching everywhere that this isn’t the case. I’m going to try again with the incoming mains off this time .

 

[danielson]

I suspect it could be as well like you. You don't have another cold main coming into the property do you?

I have just turned off incoming mains and it was the kitchen mixer tap all the water has stopped flowing out of the hot taps now which is good. I can now turn my T&P valve

Looks like I may need a new kitchen mixer tap then?

 

[SJB060685]

Taps aren't my thing. Possible to fix, or you could install non return valves on the hot and cold supplies to the taps.

 

[danielson]

Taps aren't my thing. Possible to fix, or you could install non return valves on the hot and cold supplies to the taps.

Taps aren't my thing. Possible to fix, or you could install non return valves on the hot and cold supplies to the taps.

That’s a good idea with the non return valve which, to my other half’s disappointment, is better than a new tap !

 

[SJB060685]

Probably the cheapest option to be honest

 

[danielson]

That’s a good idea with the non return valve which, to my other half’s disappointment, is better than a new ta

Taps aren't my thing. Possible to fix, or you could install non return valves on the hot and cold supplies to the taps.

If still took a good five minutes for the hot water to stop flowing - could that be a sign it’s not been done for a while?

 

[Chuck]

I have a megaflo unvented cylinder on the first floor of my property and I am trying to recharge the air gap. I have turned off the incoming cold mains valve upstream (and right next to) the pressure regulating valve and then opened the hot water taps at the lowest point in the house. The problem I am getting is that I have had the water running out of these taps for at least 10 minutes with some really loud gurgling noises from the tank while the water is running. The hot water tap flow reduced significantly and did actually stop for around 10 seconds thinking it had worked (so I can then turn the TRV valve on the side of the tank to recharge the air gap), but it suddenly started to emit more water and again didn't stop.

This is exactly what you expect to happen. The open hot tap(s) run while the system depressurises then slow(s) to a stop at which point you follow the instructions and hold the TRV open to break the vacuum and let the air space fill as the water drains under gravity.

Unless you have plumber's hands, wear a glove on the hand you are holding the TRV open with because it has a strong spring, sharp knurling and you'll need to be there for up to 20 minutes for it to complete draining.

 

[danielson]

This is exactly what you expect to happen. The open hot tap(s) run while the system depressurises then slow(s) to a stop at which point you follow the instructions and hold the TRV open to break the vacuum and let the air space fill as the water drains under gravity.

Unless you have plumber's hands, wear a glove on the hand you are holding the TRV open with because it has a strong spring, sharp knurling and you'll need to be there for up to 20 minutes for it to complete draining.

Thanks for this but it wasn’t exactly what I expected to happen…The cold from the mains mixer tap downstairs was actually feeding back into the system via the hot so without turning the mains stopcock off it would have done it forever.

Once turning off the mains supply and not just the stopcock upstream of the PRV then the hot water did stop.

Once the hot water did stop however and then I turned the TRV valve no water came out at all.