Low pressure hot water??

[dylski]

I've recently been to a job which after a couple of seconds of turning the hot water tap on the flow turns to a drip. It's an old hot water cylinder with an f & e tank. I've not worked on these much and could only think to make sure all the stop taps and service valves were open correctly and as far as I can see they are. Any ideas people??

 

[petercj]

Might be a build of scale in the bottom of the cylinder or pipes restricting flow - is it a hard water area?

 

[chris watkins]

Air-lock, have you been working on the system i.e.turned off & drained down ?? Is the cold water OK ??

 

[dylski]

No it's soft water. And the pipe work looks fine, 22mm all the way with a couple of bends. The cold water is fine and I haven't worked on it before, the customer said they moved in and that's how it was. It works fine for about 3 seconds then turns to a dribble, I'm baffled!?

 

[dylski]

If it is scale is it a case of a new cylinder?

 

[petercj]

Maybe air lock as chris has suggested - have you tried blowing out with mains pressure. If the valves have been turned off recently, maybe a sheered spindle perhaps?

 

[chris watkins]

What is the tap on & what type is it? Does the 22mm serve other fittings & are these working OK ? it can only be the pipe or the tap. Does the water come out of the tap hot within the 3 sec ?

 

[dave1]

Like others say airlock, check other taps, I've had it where the outlet on the cylinder is scaled up, also had insulation from a new cylinder getting caught at a ballofix valve, could be a dodgy tap washer, just a few ideas there lol

 

[petercj]

If there are mixer taps on the same system, try turning hot and cold on full and then block the flow with your hand for several seconds, then release, and repeat a few times.

 

[Dannyparty92]

This is a long shot but It is a possibility. In the hot water cylinder there is what's known as a sacrificial anode and a sort of large rubber washer between the anode and the cylinder wall it is possible and there have been cases of this aswell that the washer could get brittle s

 

[Dannyparty92]

And free off and move to the top of the cylinder and when someone opens the hot water draw off this washer would be sucked up where the hot water leaves the cylinder this could be what has happened