Cause of Cold Water Supply Airlock From Header Tank?

[rbz5416]

I replaced a knackered ball valve on the tank with a Torbeck. A couple of weeks later an airlock developed in the cold feed from the tank. I cleared that by pushing mains pressure back up the bathroom sink tap with the outdoor hose. Two months on & it's happened again. So I'm looking for likely the causes. The obvious of the tank emptying faster than the new valve can fill it is unlikely as it's at my mother's place. No bath just an electric shower & nothing else with the potential to drain what is a fairly large tank. The only other thing I can think of is the new valve intermittently not opening.

The only other thing maybe worthy of mentioning is the ball valve in the WC cistern is fairly slow to fill, as this is also fed from the tank. Could this be a potential source of air entering the system?

Really need to get to the bottom of it as she's a 120 mile round trip away!

 

[Chris F]

Could be grit in the torbeck? ?
I have honestly never heard of anyone putting a torbeck valve in a header tank.
Personally I would take the torbeck out and fit a part 1 or 2 ballvalve

 

[mache]

First of all not a plumber so if the following is talking rubbish then more qualified guys can inform you better. What I was wondering is you mention the WC cistern is slow to fill. I was just wondering that if the basin tap is fed from the cold water tank also, could it be after mothers done the business, flushed the loo and goes to wash her hands (quick wash with cold water) that air is being drawn back in though the still open WC cistern valve.. That being said I would have though this would have been a long standing problem and not new, unless in changing the valve you have dropped something or disturbed some debris that is now blocking the tank oulet connector causing restricted flow hence air drawn through the wc valve.

No offence if any tells me i'm talking cack...
Regards
Martin.

 

[SJB]

Get that torbeck out sharpish or you'll be up the creek sans paddle when the mains pressure spikes randomly and pops the head off it and floods the house as they're proem to do. Part 1 or 2 brass valve all the way.

If the tank isn't running dry ever then air locks shouldn't be a problem, could be a big bit of summat blocking the flow out of the tanks now and again

 

[Best]

Either fit a part 2 brass ballvalve or fit a Fluidmaster Pro (brass tail version only!).
Torbecks have become complete rubbish.

 

[rbz5416]

Thanks for all the input. No love for Torbecks then?

Had another look at it yesterday & everything seems to be working fine. Opened the valve up & flushed it through as a precaution but I'm minded to replace it as the problem only occurred after it was fitted. Really can't see the tank draining as with the bathroom tap on, the level drop was barely perceptible & it's a big tank.

What is the benefit of a brass tail on a Fluidmaster?

 

[Best]

Thanks for all the input. No love for Torbecks then?




So what is the difference between part 1 & 2 valves?


And as Best mentioned it, what is the benefit of a brass tail on a Fluidmaster?

Part 1 valves work with a piston with a small rubber washer inside it, that pushes closed against the "nozzle" part. which is worked with the arm of the valve. The water flows out the bottom of them.
Part 2 valves only use a diaphragm washer which is flexed closed against the "nozzle" part by the arm pushing a plastic pin. Water comes from the top of them, usually through a plastic screw in bend. They have less risk of water contamination - being sucked back from tank if tank is too full & mains is off & draining for any reason for example. Part 2 valves are regulation to fit, although personally I am not fond of them as they are not great quality. A part 2 valve while washer is in good order has the advantages also of generally being less noisy & no water hammer compared with part 1 valves & also a 1/2" part 2 valve can be easily changed from high pressure to low by simply replacing the nozzle part. The arm has a 90 degree bend on part 2s which is handy for adjusting the float for water level.


As to brass tails - the body of all plastic fill valves are a hard brittle & sometimes thin plastic which can crack at some time in the future & flood house outside the tank/cistern, so best the threaded bit which takes all the strain, is brass. Also very easy to strip the threads on plastic tails.

 

[rbz5416]

Part 1 valves...

Thanks for the comprehensive answer.