Tank in my bathroom question

30 May 2005
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United Kingdom
In the bathroom on the first floor of my Victorian abode is my water tank. For the past few months there has been the sound of water dripping INTO the tank from the pipe that feeds it, and when I went away for a week I returned to find a small puddle below the overflow pipe, so clearly when I use water daily I am draining enough out of the tank for it not to overflow, but when I do not then this drip, drip is enough to fill the tank. I called a decent plumber who changed the ball-cock, which as I live in Kent has over eight years of muck and deposits on it from the water that we get in this part of the world. Sadly the drip, drip in continuinng - what else could be causing the ball-cock not to seal up the flow from the pipe into the tank ... is there a washer somewhere that perhaps need replacing?
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can you see he has fitted a complete new one and not just bend the arm etc.
I stood and watch him remove the old one (covered in muck) and install the nice new one.
can't really be much if it's a new one.
could be faulty, or crud stuck in the diaphragm.

does it stop if you hold the ball up ?
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Yes it does stop when i hold it up - but I can't hold it up all of the time! I wonder if somewhere in the system there is a washer that may have worn or some other gremlin.
how long ago was the new valve fitted?

Is it brass or plastic?

A photo might help.

One reason for it dripping might be that there is a leak elsewhere and the valve is just keeping the tank topped up. Turn off the supply, pencil-mark the water level, leave it for an hour while using no water, and see if the level drops.
Maybe the float is just set a tad too high. The valve should cut off completely when the water level is a couple of inches below the overflow.
some (usually brass ones) are set by bending the arm, some (usually plastic) by adjusting a screw.

Float valves are generally very reliable, but they can start leaking at any time if a bit of grit in the water supply lodges on the valve seat, stopping it from closing fully without 'manual assistance'. Stripping and cleaming it would cure that, but is hardly worth doing compared with the price of a replacement valve.

Sometimes the float slowly fills with water and sinks. It's quite rare with plastic floats, but easy to check. Unscrew the float from the end of the arm, and give it a shake - if you hear water, it's leaking.
Yes the ball was changed - I reckon that there is a bit of grit/hard water effluent stuck somewhere - seems most odd and the drip, drip annoys me! Cheers for your help folks, much appreciated.

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