How can I eliminate play in a water tap?

Question

My hot water tap in the bathroom has had half a turn of play for as long as I can remember. That is, after increasing flow it takes half a turn before the flow will start going down again, and vice versa. It's a relatively minor problem, but it's a pet peeve of mine. The cold water tap responds instantly.

At one point I had the whole tap replaced for other reasons, and, to my dismay the replacement was exactly the same: perfect on the cold side, half a turn of play on the hot side.

I'd had enough recently and bought a spare tap gland at the local hardware store. It is now installed. The amount of play is almost exactly the same as before. I could actually feel it in the gland before installing it; it is wobbly. I'm pretty certain there is nowhere else that the play can be coming from.

Is this normal or am I really unlucky with this tap? How can I buy a gland without such wobble in it, like the one I have on the cold side? Please excuse my UK terminology.

Answer 1

From your comment, it sounds like the root issue is the lower water pressure from your hot supply. With lower water pressure, when you only slightly open the valve, there might not be enough pressure and/or flow for the water to overcome the other forces acting against it (gravity, restriction from valve, etc.). Similar to say a garden hose - with low pressure, it might not leak at all, but open the valve up all the way and it starts leaking at certain places (except in this case, the leak is the flow you want).

The first thing to check is that the shutoff for your hot water supply is fully open - at the sink, at the tank and anywhere else along the way where there might be a shutoff. If all of the shutoffs are fully open then it could be due to incorrectly sized pipes, mineral build up (depends on type of pipe). Check to see if the pressure is low at any other facuets - this will give you a good idea if its a problem with the plumbing or just that particular fixture.

Answer 2

I've had a couple of taps where I've seen something similar, and both cases the cause has been basically very cheap hardware.

You don't mention if you replace the taps with exactly the same hardware, but it might be worth a bit extra for peace of mind.

If you're purchasing good quality hardware, and still have the problem, then the problem might be else where - check to see if there are any blockages in the pipes, or anything else in the system that could be causing the problem.

Do you have an on-demand hot water heater? Any sort of recirculating pump?

Answer 3

Based on your reply to my comment, you still are using the old valve seat, the round metal part the gland pushes against to seal off the water flow. It's likely corroded and/or damaged, preventing proper, uniform control of water flow. If you remove your new tap insert and peer into the opening with a torch, you should be able to visually confirm there's an issue with the valve seat.

In theory, the valve seat can be removed and replaced, but it is usually so well corroded to the tap base housing that forced removal will likely damage the whole fixture, requiring total replacement. Because of this, there are simple surfacing tools available to refinish the valve seat surface. The tool guide fits where the insert goes. You turn the tool while applying pressure, and the corroded material is cut away, creating a fresh, clean, uniform surface.

Before you replace the insert, you should examine the gland, the corroded valve seat may have already damaged the rubber surface, requiring it to be replaced yet again. With a properly surfaced seat and smooth gland, the tap will function like it was new.