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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.

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Could it be that it's just the length of time for the water to temper after the hot/cold ratio is changed? Instant changes in water temperature usually involve return-lines to the hot-water heater. –  RI Swamp Yankee May 16 '12 at 17:28
    
@romkyns The only times I've seen that sort of thing is when the washer is crushed or there is another old washer stuck in the breaching piece thats so old and black you don't notice it till you get a torch and have a good look –  UNECS May 17 '12 at 9:25
    
If you open the hot all the way, what's the pressure like? Similar to cold, or a lot lower? –  Steven Jul 24 '12 at 16:59
    
@Steven it's a lot lower. –  romkyns Jul 24 '12 at 19:26
    
When you say you replaced the tap, was it just the upper part with the handle & shaft holding the gland, or really the whole thing, including the base part attached to the basin or wall? If the former, there may be a problem with the valve seat in the base. Otherwise, I've no idea. –  bcworkz Jul 24 '12 at 20:45
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3 Answers

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?

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Hard to say about the quality; as is typical in the UK, there's exactly one kind on sale, and it's not exactly cheap ($10). Contrary to what I said in the question, the play was actually reduced noticeably, but still nowhere close to the cold tap. Hot water is supplied from a large electric boiler; no pumps of any kind involved, just gravity. –  romkyns Jul 24 '12 at 9:40
    
@romkyns: We might want to get terms defined. The cheapest tap I can buy in Canada is about $25, and you can easily spend $200 on designer kit. Are you talking about tap, the valve (a replaceable part of the tap), a washer, or something else? –  chris Jul 24 '12 at 21:29
    
Good point; I'm referring to the "gland", i.e. one of these. This attaches very firmly to the rest of the tap, and the "handle" that goes on it has barely detectable play. The quality of the rest of the tap obviously won't contribute to the issue. –  romkyns Jul 24 '12 at 23:14
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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.

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I suppose this could be why I see the difference between hot and cold. I'll see if I can get around to swapping the valves on the hot and cold to verify whether the play moves with it, or stays on the hot side. There's only about 1m height difference between the tap and the top of the boiler, so nothing short of a pump can fix this pressure... right? –  romkyns Jul 24 '12 at 23:16
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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.

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