What might cause this tap to over-run?

[WaterTight]

After turning cold on and then off there is a 2 sec gap then for a few seconds more water comes out. Not just a few drips, not full force, somewhere in the middle. Not every time but most times.

On swan neck taps where this happens I have presumed it's water left in spout and a bit of syphonage happening. But on this tap (new, fitted by me, recently) the spout angles slightly back which I thought would discourage this and more importantly it only does it on the cold, not the hot. Futhermore it's fed from a combi so should be equal pressure?

Previous tap (near identical style, prob diff make) didn't do it.

The water doesn't mix in the spout. The hot comes from separate part of the tap that seems to be the middle of the spout, the cold from the outer part of the spout.

I have not tested the pressure. The tap is listed as having a max pressure of 4 bar. But if it was a pressure issue wouldn't it effect the hot too as its a combi? Plus it shuts off fine. It seems more like the water left in the spout is coming out, but could be wrong.

I changed the ceramic valve to another one I had on van and it did the same.

I can contact company but wanted unbiased opinions on the cause first. My guess is the larger apeture from which the cold comes is just over whatever threshold is needed for some syphonage to occur from the last few drips.

I thought (after leaving) I could have swapped hot and cold feeds round and see if it just does it from hot now. I also thought I could try fit a different aerator which requires more force for water get through.

Thanks

 

[Best]

I think your diagnosis of it being water coming back from the cold water part of spout, (partly due to that part of spout being larger) is spot on.
And you are also correct that the aerator would prevent the “water over run” if you use a fine gauze type aerator.
I have solved same problem by using a more restrictive aerator on a tap. On a high pressure hot and cold supply (like a combi system on your job) the taps are best having restrictive aerators anyway, so to reduce flow and splashing, as well as for preventing the draining of the spout.

 

[WaterTight]

Cheers Best. I will give that a go.

If it was my tap I would just live with it but nothing's too good for custards.

Hopefully the tap accepts a new aerator without a fiddle-fest.

 

[Best]

Cheers Best. I will give that a go.

If it was my tap I would just live with it but nothing's too good for custards.

Hopefully the tap accepts a new aerator without a fiddle-fest.

Some aerators are very difficult to remove or install. And then there are some taps that have a special seal that fits onto the inner pipe (hot) of the separate water of the spout.
If you know the manufacturer it would be best to contact them asking for an aerator for the tap for higher pressure.

 

[WaterTight]

So I took your advice and the manufacturer says this tap cannot have it's aerator removed/replaced. So would you a) fit a PRV after stopcock or b) change the tap?

 

[WaterTight]

Or is there some kind of restrictor that could be fitted to cold feed pipework below tap that performs job of aerator but not actually fitted on the tap? Like an in-line aerator? I tried turning the iso down which didn't make any difference.

 

[WaterTight]

Anyone ever fitted something like this?

6 Litres Per Minute In Line Tap Regulator :: Tap Aerator :: Aqualogic (WC) Ltd

 

[Best]

So I took your advice and the manufacturer says this tap cannot have it's aerator removed/replaced. So would you a) fit a PRV after stopcock or b) change the tap?

Sorry WaterTight, I was busy today and only reading your posts now.
If an aerator definitely can't be fitted to that tap, then I would replace the tap for a one that has an aerator suitable for restricting high pressure water.
The spout is the cause of the problem and only an aerator on end of spout will stop the over run.
So putting a flow restrictor on the pipework will not help. They only stop the high flow and splashing you get with some taps on high pressure.

 

[WaterTight]

Thanks Best. I've emailed the site I bought if off making my case that it's not fit for purpose as advertised (we'll see if they bite) and emailed a couple of companies that make similar ones in white to see if they either have high pressure aerators fitted or can be changed to one.

I've fitted millions of taps and not had this before but I suspect most people will just live with it and not call you back.

Incidentally, why would fitting in-line aerators to the supply feeds not do the same as fitting one at the end of the spout? I don't doubt you but wouldn't be able to explain it if asked.

 

[Best]

Fitting an aerator (fine gauze type) on the end of the spout acts as a sort of stopper holding the residue water in the spout. The water can’t freely run out under gravity pull.
Putting a flow restrictor on the pipework won’t do same and will have no effect on the tap once the tap is turned off anyway

 

[WaterTight]

Of course, yeah. Thanks.