Expansion tank keeps overflowing
Iain
System: Baxi Bermuda fire/back boiler with gravity hot water and
pumped central heating. I live in a bungalow so the hot water tank is
situated behind the boiler just the other side of the back of the fire
place, with the expansion tank in the loft immediately above it. The
chap who had the house before me would have made Heath Robinson stand
back in wonder. He put a single zone valve in the feed to the hot
water cylinder controlled by a tank stat(in much the same way as a C
plan system) but the valve did'nt have the necessary microswith, so he
did some wierd thing with a 240 volt relay and the wiring etc....
I've since rewired it without the relay and it's been working fine for
about 2 years now. Anyway to cut to the chase.
Problem: For about a month now the expansion tank has been dripping
from the overflow pipe. Immediately, I thought 'ball cock'. Ball
cock replaced, tank drained to correct level, no water coming in to
tank from ball cock. 24 hours later drip drip drip.
Ah, maybe I commited some schoolboy error when fitting the ballcock.
Ball cock off, checked, refitted, tank drained etc etc. 24 hours
later drip drip drip.
Hmmm, try to ascertain where the water is coming from, tank drained
to level, wrapped tissue paper round ball cock and joint. 12 hours
later, water level raised by some 6 cm, tissue paper as dry as,
well,tissue paper. No sign of it coming in anywhere, even from the
vent pipe.
I've even tried this with the boiler switched off for 12 hours (any
longer and 'she who must be obeyed' gets annoyed 'cos she can't have a
bath).
btw the water level never goes down as the boiler cools etc.
Now, maybe I've got some sort of perpetual water generator and I
should sell it to the water board immediately, or water is getting in
to the system somehow. Can anyone throw any light on this please
before it drives me mad hahahahah.
Thanks in advance.
Iain
Andy Hall
"Iain" <ia...@iwilkinson.plus.com> wrote in message
news:d2e10365.02062...@posting.google.com...
> Hi all, I wonder if anyone has a solution to my problem?
>
>
> Problem: For about a month now the expansion tank has been dripping
> from the overflow pipe. Immediately, I thought 'ball cock'. Ball
> cock replaced, tank drained to correct level, no water coming in to
> tank from ball cock. 24 hours later drip drip drip.
>
> Ah, maybe I commited some schoolboy error when fitting the ballcock.
> Ball cock off, checked, refitted, tank drained etc etc. 24 hours
> later drip drip drip.
>
> Hmmm, try to ascertain where the water is coming from, tank drained
> to level, wrapped tissue paper round ball cock and joint. 12 hours
> later, water level raised by some 6 cm, tissue paper as dry as,
> well,tissue paper. No sign of it coming in anywhere, even from the
> vent pipe.
>
> I've even tried this with the boiler switched off for 12 hours (any
> longer and 'she who must be obeyed' gets annoyed 'cos she can't have a
> bath).
>
> btw the water level never goes down as the boiler cools etc.
>
> Now, maybe I've got some sort of perpetual water generator and I
> should sell it to the water board immediately, or water is getting in
> to the system somehow. Can anyone throw any light on this please
> before it drives me mad hahahahah.
>
I don't think you are going to like this. It would appear that you have
diagnosed that there is a leak between the primary and
secondary water circuits - i.e. the coil in the DHW cylinder. This is the
only possible source of water assuming you have eliminated the expansion
tank as carefully as it appears you have.
When everything is quiet, take a look at the ball valve in the storage tank
and see if water is dripping in. Bear in mind though, that in the larger
tank it will be longer before the level drops enough for the valve to open.
If this is right, then it's new cylinder time, so you have the opportunity
to convert the system to fully pumped and to use a fast recovery cylinder.
That will earn you many toady points with the bath loving SWMBO.
.andy
Roger Mills
What do you regard as the *correct* level? The expansion tank is - by
definition - intended to deal with the fact that the relatively fixed amount
of water in your boiler/radiators/primary hot water circuit EXPANDS when it
gets hot, and has to have somewhere to go. The level at cold therefore needs
to be pretty low, in order to ensure that the hot level is still below the
overflow.
I suspect that your cold level is too high - it only needs a couple of
inches in the bottom of the tank, as long as it covers the feed pipe going
out of the bottom.
If you block up the overflow, does it go on getting higher and higher, or
does it settle at a level just above the overflow? If the latter, that
confirms my view that the cold level is too high. However, if the former,
there must be an internal leak in your hot water cylinder which is allowing
domestic hot water to get into the heating coil. If this is the case, you
will need a new indirect cylinder.
HTH,
Roger
Mark Lex
The problem is in your hot water cylinder. The heat exchanger coil has
perforated and water is getting from the secondary water (DHW) to the
primary water (CH)
Dave Liquorice
> Hmmm, try to ascertain where the water is coming from, tank drained
> to level, wrapped tissue paper round ball cock and joint. 12 hours
> later, water level raised by some 6 cm, tissue paper as dry as,
> well,tissue paper. No sign of it coming in anywhere, even from the
> vent pipe.
Sounds like a (small) leak in the heat exchanger coil in the HW
cylinder. I guess that the level of water in the HW header tank is
higher than that in the CH header tank.
The bad news is that such a leak means a new cylinder.
--
Cheers new...@howhill.com
Dave. Remove "spam" for valid email.
Iain
problem lay. Looks like I'm getting down and dirty with the plumbing
tools again and changing the hot water tank then (checked Wickes today
a replacement costs around £100). Ho hum..... I was looking
something to do next weekend.
Regards.
Iain
Brian S Gray
You might find it could be cheaper at a builder's merchant - and do
not forget that the copper tank you take out might be worth a few
pounds from a scrap merchant.
Roger Mills
Brian S Gray <ban...@tamaris.u-net.com> wrote in message
news:3d1f63ae...@news.u-net.com...
Screwfix are selling the latest energy efficient ones for £79.99 (if 900 x
450 is the size you want).
Roger
Frank Erskine
<ban...@tamaris.u-net.com> writes
>You might find it could be cheaper at a builder's merchant - and do
>not forget that the copper tank you take out might be worth a few
>pounds from a scrap merchant.
Apparently not nowadays. I had my whole heating system replaced a couple
of weeks ago and I had to persuade the installers to take away the old
piping and cylinder :-)
--
Frank Erskine
Paul W
"Roger Mills" <roger...@hampton-magna.freeserve.nospam.uk> wrote in
message news:afnpsk$cho$1...@newsg3.svr.pol.co.uk...
Tanks come in different "grades" make sure any tank you buy is "grade 3" and
kitemarked. The non gradded tanks are thinner and may have a smaller coil.
BTW the going rate for a scrap cylinder is under £4.
Paul.
Christian McArdle
and
>kitemarked. The non gradded tanks are thinner and may have a smaller coil.
I thought they are all "Part L" now. Rapid recovery and insulation are
legally mandated. (Since April 2002).
You should certainly convert from gravity to pumped, if the boiler allows
it.
Christian.