Float valve problems

Freddythefearlessfish

Can I get some opinions please.  The float valve went in my central heating water tank about a year ago (after many years) and so I replaced it with https://www.toolstation.com/made4trade-float-valve-part-1/p39573  however, just under a year later the new valve has gone again.  This time causing severe hammer, something I've not been familiar with before, however, finally tracked down the culprit (after isolating it the problem is fixed - temporarily at least - though currently I only have a fixed amount of water in the central heating water tank - very far from ideal).

So my question is - why would a new float valve have gone so quickly?

1.  I bought a dud.  Therefore solution is buy another one it'll only cost me a fiver and I know an exact replacement is guaranteed to fit perfectly.
2.  Toolstation Made4trade products are rubbish.  Don't buy cheap when they can lead to serious damage.  Instead buy a quality product such as [please insert quality brand or link].
3.  There is a likely to be to fundamental problem with the water pressure in the house, get a plumber to investigate, since fixing the weakest point is only going to cause a system to blow somewhere else - quite likely somewhere a lot harder to access than the hot water tank, which could prove very expensive.

GDB2222

You replaced the float as well as the valve?  Not convinced that would cause hammer, though.


I am perplexed, as the valve on an expansion tank should hardly ever open, anyway. What’s gone on it?

ThisIsWeird

FtFF, I suspect, like GDB, that there's summat else amiss.

This is def the ball valve in the SMALL F&E tank? In which case, it should hardly ever open to top up that tank. If it's topping up regularly, then you have an issue that needs sorting - a leak, or possibly an overheating system. So that's the first Q to ask.

As for 'hammer',  what exactly do you mean? ONE big thump in the pipes as the valve shuts off? Or a foghorn? Or a repeated stammering noise? 

As for the quality of the BV, I suspect it's as good as any such brass valve. 

molerat

A bit of grit / sand stuck in the valve is a common problem

plumb1_2

molerat said:

A bit of grit / sand stuck in the valve is a common problem

Correct, and most probably just needs a new washer and maybe valve seating.
Plus it’s the wrong ball valve, it should be a Part 2 valve.

Freddythefearlessfish

ThisIsWeird said:

FtFF, I suspect, like GDB, that there's summat else amiss.

This is def the ball valve in the SMALL F&E tank? In which case, it should hardly ever open to top up that tank. If it's topping up regularly, then you have an issue that needs sorting - a leak, or possibly an overheating system. So that's the first Q to ask.

As for 'hammer',  what exactly do you mean? ONE big thump in the pipes as the valve shuts off? Or a foghorn? Or a repeated stammering noise? 

As for the quality of the BV, I suspect it's as good as any such brass valve. 

Correct.  Agree it should hardly ever open.  As far as I'm aware it wasn't regularly, or ever topping up to my knowledge.

As for my description of hammer.  After a full reset (turning off the stop !!!!!! draining from the top tap, down the bottom tap in the house, and then turning the the stop !!!!!! back on, running the taps for a bit, getting everything back to hunky dory) I was getting a single thump.  About a week later I was getting serious hammer every time the cold water was turned off - foghorn like.

Thanks for the pointer that the quality is likely to as good as any other.

Freddythefearlessfish

GDB2222 said:

You replaced the float as well as the valve?  Not convinced that would cause hammer, though.


I am perplexed, as the valve on an expansion tank should hardly ever open, anyway. What’s gone on it?

No.  Float is the same float as original.

In terms of what I observed.  When I was getting the severe hammer I was able to observe the valve spluttering like it was struggling in an attempt to let air in!  Very odd, the water in the tank was full.  The valve appeared to be allowing a tiny amount of water out, then gulping for air, then letting a tiny bit more water out.  The water was gently running out of the overflow.

Freddythefearlessfish

molerat said:

A bit of grit / sand stuck in the valve is a common problem

molerat said:

A bit of grit / sand stuck in the valve is a common problem

This sounds really interesting and feasibly worth me taking the valve out and having a proper look.

Freddythefearlessfish

plumb1_2 said:

molerat said:

A bit of grit / sand stuck in the valve is a common problem

Correct, and most probably just needs a new washer and maybe valve seating.
Plus it’s the wrong ball valve, it should be a Part 2 valve.

Interesting indeed.  Thanks.  Seems you agree that it may be a common problem - I wouldn't be surprised at their being dust trapped at all, where it is seated.

As for the Part 2 valve - how much does this matter?  To be fair for an extra 2 quid it would be worth getting the right valve.

plumb1_2

The tank shouldn’t be full log water, have it set min 50mm below the warning/ overflow pipe outlet 

Section62

Freddythefearlessfish said:

In terms of what I observed.  When I was getting the severe hammer I was able to observe the valve spluttering like it was struggling in an attempt to let air in!  Very odd, the water in the tank was full.  The valve appeared to be allowing a tiny amount of water out, then gulping for air, then letting a tiny bit more water out.  The water was gently running out of the overflow.

Is the supply side pipework rigdly-fixed, or is it free to flop around?

Float valves in cisterns can suffer from resonance, where the valve body and cistern/tank wall it is fixed to move, causing the valve to open just enough to let a small amount of water out.  This in turn can set up ripples on the water surface which makes the valve alternately open and close.  It tends to be an issue on more flexible plastic tanks/cisterns rather than galvanised steel/asbestos types used in the past.

If the pipework isn't rigidly-fixed then it is possible water use elsewhere in the house (including the cold water storage tank if you have one) is pushing/pulling on the supply pipework to the F&E tank, and this is creating the unwanted effect.

If the flow cut-off level is close to the warning pipe level then this effect could be sustained over a long period of time - as the excess water can drain away allowing the 'just wrong' conditions to continue.

If the warning pipe is about 50mm above the cut-off level as plumb1_2 suggests, the force on the float should be sufficient to break the cycle before the water level reaches the warning pipe level.

If the supply pipework seems floppy then try fixing it more rigidly and see what happens.  In doing so, avoid applying too much force to the pipes, especially plastic ones, as this could cause joints to fail.