Repairing Ballvalves


Float-operated valves — ballvalves — are the simple devices that control the flow of water into cold storage tanks, central heating feed and expansion tanks, and toilet cisterns. Like taps, they are in more or less constant use, so it’s not surprising that problems sometimes occur.

Check the chart shown below for symptoms of faults and their likely causes. Leaking overflows need urgent attention, since what starts as a tell-tale drip can quickly develop into a flood — most overflows can’t cope with a full-scale flow of water (strictly speaking they are only warning pipes). The leak may also give rise to damp problems on the wall below.



Valve lets water by, causing overflow: Washer/diaphragm worn

Seat cracked by frost

Valve mechanism jammed due to scale

Leaking float

Valve corroded due to dezincification

Service valve

Service valve

Service valve or replace

Empty float and seal or replace

Replace valve with dezincification-resistant type

Valve won’t let water by, causing tank to empty: Valve jammed due to lack of use (very common on C.H. feed and expansion tanks) Service valve
Tank slow to fill Valve outlet blocked with grit

Wrong seat or valve

Service valve

Replace seat or valve

Excessive noise from valve a tank fills Wrong seat or valve

Worn valve

Water hammer due to high pressure

Float bounding on surface of water

Replace seat or valve

Service or renew valve

Turn down pressure or fit different valve

Fit damper to float

Before you start a repair of your broken ballvalve, identify what sort of valve you are dealing with (see below) and make sure that the shops are open — you may have to take the valve with you to get replacement parts. Don’t forget that the water will have to stay off in the meantime.

piston valve and diaphragm valve




All ballvalves work on the same basic principle: an air-filled float, attached to the valve via an arm, rises and falls with the water level in the tank.

Attached to the arm inside the valve is a plunger and plastic diaphragm (diaphragm type), or a piston with a rubber washer (piston type), which closes off the water supply when the level is at the right height.

25. May 2011 by admin
Categories: Plumbing | Tags: , | Comments Off on Repairing Ballvalves


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