upstairs airlock

[wildcard]

Went out to a customer today who had no cold water upstairs,put my wet vac on cold tap drew the water through job done. My question is why would this suddenly just happen,I know that it could be up & down pipework in loft.
The cold service did not run down in airing cupboard,it rang along loft & down in bathroom in boxing.
Thanks

 

[SimonG]

Badly run pipework. Incoming float valve not running quick enough and ran tank out of water.

 

[GasmanxxxR1]

As above really, have they got a powerful shower and other stuff running the tank dry

 

[wildcard]

Just a basic set up really ,no shower pumps.50 gallon tank.