At college, we've been informed that, "the trick about this tap is to avoid
tightening the hot water tap as it has been designed to drip, something to
do with the working system of the water boiler."

Could this be true?

Many thanks

Martin

At college, we've been informed that, "the trick about this tap is to
avoid tightening the hot water tap as it has been designed to drip,
something to do with the working system of the water boiler."

Could this be true?

It is true about some cheaper point of use storage electric water heaters.
These heat a small store of water for basins (i.e. in loft conversions)
where hot water is not otherwise available, or would have an excessive dead
leg that no-one would bother to clear.

If they don't have an internal expansion vessel, then the actual tap is used
to relieve the pressure rise when the water is heated. I'm guessing a bit
here, but I suspect the taps actually control the input to the heater. The
tap spout is left connected and unvalved to the heater as a vent. This would
basically mean the heater is vented when the tap is off, and pressurised
when the tap in on. Obviously, proprietary taps must be used for this.

When the water is being heated, some will drip from the tap as it expands.

Christian.

In article ,
Christian McArdle wrote:
I'm guessing a bit here, but
I suspect the taps actually control the input to the heater. The
tap spout is left connected and unvalved to the heater as a vent.
This would basically mean the heater is vented when the tap is off,
and pressurised when the tap in on. Obviously, proprietary taps must
be used for this.

When the water is being heated, some will drip from the tap as it
expands.

Exactly so: we have a notice on a PoU water heater in our church
kitchen explaining this. I don't know when they changed the rules but
the modern ones can be used with ordinary taps with the expansion being
taken up by the feed pipe if long enough, or expansion vessel if not.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm

the modern ones can be used with ordinary taps with the expansion being
taken up by the feed pipe if long enough, or expansion vessel if not.

Not sure about that. The one I just fitted has a 3 bar pressure relief valve
which you are supposed to vent somewhere safe

"Tony Bryer" wrote in message
...
In article ,
Christian McArdle wrote:
I'm guessing a bit here, but
I suspect the taps actually control the input to the heater. The
tap spout is left connected and unvalved to the heater as a vent.
This would basically mean the heater is vented when the tap is off,
and pressurised when the tap in on. Obviously, proprietary taps must
be used for this.

When the water is being heated, some will drip from the tap as it
expands.

Exactly so: we have a notice on a PoU water heater in our church
kitchen explaining this. I don't know when they changed the rules but
the modern ones can be used with ordinary taps with the expansion being
taken up by the feed pipe if long enough, or expansion vessel if not.

The ones which use the mains pipe for expansion (and some combi boilers too)
will have a warning that they're not to be used without adding an expansion
vessel if there's a check valve or loose-jumper stopcock upstream of it. Of
course when someone comes along and fits a check valve or whatever they
probably don't think to check what's downstream of it ...

"Tony Bryer" wrote in message
...
In article ,
Christian McArdle wrote:
I'm guessing a bit here, but
I suspect the taps actually control the input to the heater. The
tap spout is left connected and unvalved to the heater as a vent.
This would basically mean the heater is vented when the tap is off,
and pressurised when the tap in on. Obviously, proprietary taps must
be used for this.

When the water is being heated, some will drip from the tap as it
expands.

Exactly so: we have a notice on a PoU water heater in our church
kitchen explaining this. I don't know when they changed the rules but
the modern ones can be used with ordinary taps with the expansion being
taken up by the feed pipe if long enough, or expansion vessel if not.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm



Indeed if TB attends the CGS at CB then I put the notice there! However
I've been trying to find out for years how to repair this 'pressure release
tap' as it's very stiff. I was quoted over £80 for a replacement a few
years ago. Needless to say it's still stiff and drips for about 10 minutes
until the heater turns off!

Peter

In article , OldScrawn
wrote:
the modern ones can be used with ordinary taps with the expansion
being taken up by the feed pipe if long enough, or expansion
vessel if not.

Not sure about that. The one I just fitted has a 3 bar pressure
relief valve which you are supposed to vent somewhere safe

That's there as a safety measure if things go wrong (i.e. the stat
fails or you haven't provided the required length of feed pipe or
expansion vessel) not to handle normal expansion

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm

Martin Sewell wrote in
. 13.2:

At college, we've been informed that, "the trick about this tap is to
avoid tightening the hot water tap as it has been designed to drip,
something to do with the working system of the water boiler."

Many thanks for your replies! :-)

Regards

Martin