Airlock?

[Ryler]

The cold water cistern was drained down to fix a tiny crack in the plastic.
Refilled and now the bath and wash hand basin cold taps have stopped working.
Just a tiny dribble from the bath cold.

Tried mains pressure to blow out an air lock and just got blasted in the face with water as though the tap was turned off. (old gravity feed taps)
Any ideas.
The guy is without bathroom water since saturday.
I was only there to platform the loft for a new set up.
The guy drained it down himself.
All I did was apply some mastic to stop the leak.

 

[Nozzle]

Scale/silt sucked through the pipe from the head tank. Now blocking somewhere.

Nozzle

 

[Elkato531]

Check the pipe runs from the loft. Sometimes there is a section that's horizontal or slightly uphill. Just simply lifting the pipe to allow air to rise back to the tank is sometimes all that's needed.
You can also try a wet vac on the tap to pull the air lock through. It could be sediment from the bottom of the tank causing blockage. This would normally block where there is a restriction (isolation valves or under tap washers is possible).
Was the gate valve closed at any point? Is it fully open now. Old ones can break inside and not open again.
I did once have to disconnect the mains supply to the tank and attach a length of hosepipe to it. I stuffed the other end down through the tank outlet and pushed some mains pressure water through.

 

[Ryler]

Plumber was on site this morning.
He pushed the mains hose down the cold inlet at the cistern and flushed from there.
Seems it was an air lock. I'm told.

Am mystified as to why it didn't flush from the tap end.
Unless the original plumber had a non return valve fitted somewhere.

 

[denso13]

Am mystified as to why it didn't flush from the tap end.

You mentioned they are old gravity fed taps which could have loose jumpers in them. If you try to push water up through them you can't, the jumper may drop and close them off.

 

[HERTS P&D]

The cold water cistern was drained down to fix a tiny crack in the plastic. All I did was apply some mastic to stop the leak.

Where was the crack? was it below the water line?

Andy

 

[Ryler]

Beside the cold outlet.

 

[HERTS P&D]

So how did the customer know it was cracked?

Andy

 

[Ryler]

They didn't.

 

[HERTS P&D]

So what made you go into the loft?

Andy

 

[denso13]

So what made you go into the loft?

I was only there to platform the loft for a new set up.

 

[Ryler]

What is this?
The spanish inquisition?

 

[HERTS P&D]

Jesus wept, it's like pulling teeth.

So there was no leak, you went into the loft to: 'I was only there to platform the loft for a new set up'

They had a plumber on site but you filled a crack in the CWST, if it was new then it should of being replaced by the plumber.

Andy

 

[Ryler]

Water was coming down the wall.

 

[HERTS P&D]

Water was coming down the wall.

So you fixed a new CWST with silicone?

Andy