Anyone know much about these?

Place I work at has 6 'pairs' if these, installed in a new toilet block less
than 2 months ago (not by me) and already 4 of the hot taps have failed by
staying on - defeating the purpose of installing them.

Long story, but they can't be sent back to the supplier under warranty.

I've had one apart, no obvious scale, nothing seems wrong, tried lubricating
them, no real difference.

Cheapest replacements I can find are from Toolstation @ £13 a tap, so £150+
to replace them all.

Would it be temperature or pressure related?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

On Tue, 17 Aug 2010 18:24:56 +0100, The Medway Handyman wrote:

Anyone know much about these?

You mean the taps that you push on and then they run for a certain
amount of time then turn off automagically?

Place I work at has 6 'pairs' if these, installed in a new toilet block
less than 2 months ago (not by me) and already 4 of the hot taps have
failed by staying on

Only hot? Seems a bit odd can you find any specification for them?
Though if they come with red and blue inserts I'd be surprised if the
hot water was a problem, at least at hand tolerable temperatures...

I suspect they work in a similar manner to an equilibrium (torbeck
type) cistern valve. As they are failing on I suspect the small (read
tiny) passage way from the supply side to the other side of the
diaphragm is blocked thus the pressure doesn't build up to flip it
into it's other stable state and turn off the water flow. I'd also
expect there to be an adjustment but if my experience of the
pneumatic light switches is anything to go by a tiny fraction of a
turn makes a massive difference to the delay.

--
Cheers
Dave.

Dave Liquorice wrote:
On Tue, 17 Aug 2010 18:24:56 +0100, The Medway Handyman wrote:

Anyone know much about these?

You mean the taps that you push on and then they run for a certain
amount of time then turn off automagically?

Yup.

Place I work at has 6 'pairs' if these, installed in a new toilet
block less than 2 months ago (not by me) and already 4 of the hot
taps have failed by staying on

Only hot? Seems a bit odd can you find any specification for them?

Alas not :-(

Though if they come with red and blue inserts I'd be surprised if the
hot water was a problem, at least at hand tolerable temperatures...

Others I bought come as single with red or blue inserts, so I suspect the
tap is the same for both.

I suspect they work in a similar manner to an equilibrium (torbeck
type) cistern valve. As they are failing on I suspect the small (read
tiny) passage way from the supply side to the other side of the
diaphragm is blocked thus the pressure doesn't build up to flip it
into it's other stable state and turn off the water flow.

Didn't spot a diaphragm when I stripped one. Seems to be done by a spring.

I'd also
expect there to be an adjustment but if my experience of the
pneumatic light switches is anything to go by a tiny fraction of a
turn makes a massive difference to the delay.

Know what you mean. Can't find any obvious adjustment either.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

On Aug 18, 5:24 am, "The Medway Handyman" davidl...@no-spam-
blueyonder.co.uk wrote:

I've had one apart, no obvious scale, nothing seems wrong, tried lubricating
them, no real difference.

We had two of those. There was a tiny airbleed hole and a spring.
They almost never worked properly and required constant adjustment.
They were also very expensive.
Someone stole them together with all the copper they could find.
We don't have outside taps any more.

At another site, all taps have been replaced with taps with a sensor.
They work well until there is a power cut. Then as well as being in
the dark, you can't wash your hands.

"Matty F" wrote in message
...
On Aug 18, 5:24 am, "The Medway Handyman" davidl...@no-spam-
blueyonder.co.uk wrote:

I've had one apart, no obvious scale, nothing seems wrong, tried
lubricating
them, no real difference.

We had two of those. There was a tiny airbleed hole and a spring.
They almost never worked properly and required constant adjustment.
They were also very expensive.
Someone stole them together with all the copper they could find.
We don't have outside taps any more.

At another site, all taps have been replaced with taps with a sensor.
They work well until there is a power cut. Then as well as being in
the dark, you can't wash your hands.

A place where I worked did a major refurbishment of the staff loos and
installed sensor taps. Stupidly, they set them up so that taps ran for a
fixed length of time; which was too long for a quick splash of wet, and too
short for a proper scub with soap and a full rinse.
Result is either lots of wasted water when only a splash was needed; or
having to run the taps twice with even more waste of water when rinsing off
the last of the soap.

I've no idea why they didn't go for a proximity sensor that only ran when it
was needed

OG wrote:

I've no idea why they didn't go for a proximity sensor that only ran when it
was needed

You need to make sure it has a maximum "on" time. Miscreants have
discovered that, in some cases, if you cling film the sink, the
movement of water on film can be sufficient to trigger the tap.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

On Aug 17, 6:24*pm, "The Medway Handyman" davidl...@no-spam-
blueyonder.co.uk wrote:
Anyone know much about these?

Place I work at has 6 'pairs' if these, installed in a new toilet block less
than 2 months ago (not by me) and already 4 of the hot taps have failed by
staying on - defeating the purpose of installing them.

Long story, but they can't be sent back to the supplier under warranty.

I've had one apart, no obvious scale, nothing seems wrong, tried lubricating
them, no real difference.

Cheapest replacements I can find are from Toolstation @ £13 a tap, so £150+
to replace them all.

Would it be temperature or pressure related?


You don't say what make they are. I've dozens of them on a caravan
site -- all Prestex. I suspect you may be dealing with a cheaper
type. The Prestex ones are good, but didn't come out from the factory
well set up. The head on some batches was under such torque that it
took major effort with the tap body held in a large vice to get the
head out of the body. More to the point, there was a problem with
the piston in the base of the head eventually binding on the walls of
the cylinder. Solved by cleaning, rubbing down with metal polish,
cleaning again and lubricating with wax. They haven't given trouble
for years and years since. There are two washers in that design and
both are rather difficult to obtain. They need protection from frost,
but otherwise they're fine.

How about describing make and obvious parts? Do they have a cylinder
and piston? If so, does the piston move smoothly and easily in the
cylinder?

John MacLeod wrote:
On Aug 17, 6:24 pm, "The Medway Handyman" davidl...@no-spam-
blueyonder.co.uk wrote:
Anyone know much about these?

Place I work at has 6 'pairs' if these, installed in a new toilet
block less than 2 months ago (not by me) and already 4 of the hot
taps have failed by staying on - defeating the purpose of installing
them.

Long story, but they can't be sent back to the supplier under
warranty.

I've had one apart, no obvious scale, nothing seems wrong, tried
lubricating them, no real difference.

Cheapest replacements I can find are from Toolstation @ £13 a tap,
so £150+ to replace them all.

Would it be temperature or pressure related?


You don't say what make they are. I've dozens of them on a caravan
site -- all Prestex. I suspect you may be dealing with a cheaper
type.

Alas no idea what make. I suspect you are right.

The Prestex ones are good, but didn't come out from the factory
well set up. The head on some batches was under such torque that it
took major effort with the tap body held in a large vice to get the
head out of the body. More to the point, there was a problem with
the piston in the base of the head eventually binding on the walls of
the cylinder. Solved by cleaning, rubbing down with metal polish,
cleaning again and lubricating with wax. They haven't given trouble
for years and years since. There are two washers in that design and
both are rather difficult to obtain. They need protection from frost,
but otherwise they're fine.

How about describing make and obvious parts? Do they have a cylinder
and piston? If so, does the piston move smoothly and easily in the
cylinder?

Little chance of finding the make due to a supply chain problem. On
dismantling they seem fine. I'll try & take some pickys of one in bits.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk