Nrv on vent?

[xr4x4]

Hi,

Why would a non return valve be fitted on the vent just before the cws on a direct cylinder?

Cheers

 

[Dan Robinson]

Because the fitter was an idiot, and there might have been a pump somewhere on the system.

 

[xr4x4]

Doing a bathroom in 1960s flat this week, been doing plumbing, penny didn't drop with nrv on vent, arrow pointing into the cold water tank.

Drained the cold water tank, re plumbed the bathroom, Refilled, got everything working, no leaks, lovely.

Turned the valves off, hot and cold to deal with another issue in the flat, water wouldn't stop flowing so checked the hot tank....EEK..flipping things imploded..!... Bad...

Turned everthing back on slowly, it regained it shape with lots of twangs and bangs, everything looked ok, brushed sweat off my brow....nope.. Tanks spilt and leaking.

Drained it down with hose from drain off and it started imploding again.... ****!

Suddenly a bag of coins fell on my head and rushed up to the loft to crack open the nut.. Hammered the pipe off the nrv and an almighty whoosh came from the pipe.

Valve looked like it had been there since it was built.

Why?

 

[Bitzerdisandat]

As Dan said, the fitter was an idiot. That's why the tank imploded. The issue is that they had an issue with air being drawn into the system through the vent. So instead of sorting the problem, they relieved the symptom. The answer is to uprate the cold feed from 22 to 28. John...