Dear all,

I need some help diagnosing a problem I have with my hot water system.

I've got a cylinder tank in the airing cupboard which has above it two
square tanks, one large one small. I believe the larger is called the
feeder tank. As hot water is drained from the cylinder tank water is
drained from the feeder tank into they cylinder, which in turn is filled
up from the cold water mains supply up until a certain level (about a
1.5 inches below the overflow) at which point the float valve closes.

This all seems to work as described. If I don't use any hot water for
about 4 hours though the water level in the feeder tank has reached the
overflow and starts trickling out. It's a tiny, tiny trickle, so much so
that the water doesn't pour out of the end of overflow pipe but trickles
out the end, back along the bottom and is absorbed by the wall. The
plaster on that wall is blown. :-(

At first I thought that the float valve was shot, so I put in a
replacement, but that hasn't changed anything.

Any ideas as to what the problem might be, or what I should try next?

Many thanks

Andrew

Subject: Hot water system problem...
From: Andrew L VE_THIS_SPAM_STOPPERcom
Date: 08/09/04 09:09 GMT Daylight Time
Message-id:

Dear all,

I need some help diagnosing a problem I have with my hot water system.

I've got a cylinder tank in the airing cupboard which has above it two
square tanks, one large one small. I believe the larger is called the
feeder tank. As hot water is drained from the cylinder tank water is
drained from the feeder tank into they cylinder, which in turn is filled
up from the cold water mains supply up until a certain level (about a
1.5 inches below the overflow) at which point the float valve closes.

This all seems to work as described. If I don't use any hot water for
about 4 hours though the water level in the feeder tank has reached the
overflow and starts trickling out. It's a tiny, tiny trickle, so much so
that the water doesn't pour out of the end of overflow pipe but trickles
out the end, back along the bottom and is absorbed by the wall. The
plaster on that wall is blown. :-(

At first I thought that the float valve was shot, so I put in a
replacement, but that hasn't changed anything.

Any ideas as to what the problem might be, or what I should try next?

Many thanks

The overflow should vent outside and there should be enough downslope on it so
that water can't run back down the pipe. As to why the level rises there are a
couple of possibilities.

1) Hot water expands so you tend to find the level in the header tank rises a
bit anyway as the cylinder heats up. Set the float position lower. 3 or 4
inches below the overflow is about right. 1.5 is too close. If the float arm is
plastic there should be an adjusting screw on it and you just bend the brass
ones by hand.

2) If there is a steam vent pipe from the cylinder to the header tank does any
water trickle from that? A pump on too high a setting or a badly installed
system can lead to this.

--
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)

"Andrew L" com wrote in
message ...

snipped but trickles
out the end, back along the bottom and is absorbed by the wall. The
plaster on that wall is blown. :-(

Can I suggest as a temporary measure until the problem is cured, that you
tie a little bit of thin string or strong cotton around the outlet of your
overflow pipe so that the trickle is drawn down the string and clear of your
wall.
Regards
Tom

Dave Baker wrote:
The overflow should vent outside and there should be enough downslope on it so
that water can't run back down the pipe. As to why the level rises there are a
couple of possibilities.

Sorry, I probably wasn't clear on that point. The water leaves the
feeder tank via the overflow. The volume of water is so small that when
it gets to the end of the overflow pipe outside the house it goes down
the cross section of the pipe, back along the underside of the outside
of the pipe until it gets absorbed into the wall. I guess any physicists
here will be able to explain it in terms of surface tension?


1) Hot water expands so you tend to find the level in the header tank rises a
bit anyway as the cylinder heats up. Set the float position lower. 3 or 4
inches below the overflow is about right. 1.5 is too close. If the float arm is
plastic there should be an adjusting screw on it and you just bend the brass
ones by hand.

I'll set it to around 3/4 inches below the overflow.

2) If there is a steam vent pipe from the cylinder to the header tank does any
water trickle from that? A pump on too high a setting or a badly installed
system can lead to this.

I haven't seen any water coming from the vent pipe, but I will keep an
eye on it just in case. I'll let you know what I find out.

Thanks for your help,

Andrew

Tom wrote:
Can I suggest as a temporary measure until the problem is cured, that you
tie a little bit of thin string or strong cotton around the outlet of your
overflow pipe so that the trickle is drawn down the string and clear of your
wall.

What a neat idea! Thanks.

Andrew

"Tom" wrote
| "Andrew L" wrote
| snipped but trickles
| out the end, back along the bottom and is absorbed by the wall. The
| plaster on that wall is blown. :-(
| Can I suggest as a temporary measure until the problem is cured,
| that you tie a little bit of thin string or strong cotton around the
| outlet of your overflow pipe so that the trickle is drawn down the
| string and clear of your wall.

Or, as it's probably a plastic pipe, form a little lip at the base of the
pipe using pliers and the heat from eg a cigarette lighter. Or push an elbow
fitting on to the end.

Owain

"Andrew L" com wrote in
message ...
Dear all,

I need some help diagnosing a problem I have with my hot water system.

I've got a cylinder tank in the airing cupboard which has above it two
square tanks, one large one small. I believe the larger is called the
feeder tank. As hot water is drained from the cylinder tank water is
drained from the feeder tank into they cylinder, which in turn is filled
up from the cold water mains supply up until a certain level (about a
1.5 inches below the overflow) at which point the float valve closes.

This all seems to work as described. If I don't use any hot water for
about 4 hours though the water level in the feeder tank has reached the
overflow and starts trickling out. It's a tiny, tiny trickle, so much so
that the water doesn't pour out of the end of overflow pipe but trickles
out the end, back along the bottom and is absorbed by the wall. The
plaster on that wall is blown. :-(

At first I thought that the float valve was shot, so I put in a
replacement, but that hasn't changed anything.

If you have replaced the float valve AND there is no sign of it dripping
when up to level then you may have a leak in the coil inside the cylinder
which is allowing water from the heating system to make its way through into
the hot water (tap) side. This may be evident from a dribble from the
heating header tanks ball float valve without attendant rising level in that
tank.
If this is the case then you will have to replace the cylinder. Continued
leakage will cause damage to the inside of your boiler and rads etc and
contaminate your hot tap water

John wrote:

If you have replaced the float valve AND there is no sign of it dripping
when up to level then you may have a leak in the coil inside the cylinder
which is allowing water from the heating system to make its way through into
the hot water (tap) side. This may be evident from a dribble from the
heating header tanks ball float valve without attendant rising level in that

But only if the CH F&E cistern is at a higher level then the DHW
cistern, surely. If both cisterns are standing on the same platform
that the flow would go the other way, would it not?

--
Andy

John wrote:
If you have replaced the float valve AND there is no sign of it dripping
when up to level then you may have a leak in the coil inside the cylinder
which is allowing water from the heating system to make its way through into
the hot water (tap) side. This may be evident from a dribble from the
heating header tanks ball float valve without attendant rising level in that
tank.
If this is the case then you will have to replace the cylinder. Continued
leakage will cause damage to the inside of your boiler and rads etc and
contaminate your hot tap water

John - thanks. Tonight I'll stop the cold water feed to the feeder tank
just to double double confirm that it's not coming from the float valve
(I'm 99% sure it's not, but could be that the replacement, though new,
is faulty)

Andrew.

"Andy Wade" wrote in message
...
John wrote:

If you have replaced the float valve AND there is no sign of it dripping
when up to level then you may have a leak in the coil inside the
cylinder
which is allowing water from the heating system to make its way through
into
the hot water (tap) side. This may be evident from a dribble from the
heating header tanks ball float valve without attendant rising level in
that

But only if the CH F&E cistern is at a higher level then the DHW
cistern, surely. If both cisterns are standing on the same platform
that the flow would go the other way, would it not?


Thats why I said "may" have a leak

I need some help diagnosing a problem I have with my hot water system.

This might be a long shot, but hey, i`ll give it a go :-}

Do you have any hot taps or pipework above the level of the tank ?

I`m thinking if the water might be siphoning back to the tank for some
reason...

--
Please add "[newsgroup]" in the subject of any personal replies via email
--- My new email address has "ngspamtrap" & @btinternet.com in it ;-) ---

Andrew L wrote:
I've got a cylinder tank in the airing cupboard which has above it two
square tanks, one large one small. I believe the larger is called the
feeder tank. As hot water is drained from the cylinder tank water is
drained from the feeder tank into they cylinder, which in turn is filled
up from the cold water mains supply up until a certain level (about a
1.5 inches below the overflow) at which point the float valve closes.

This all seems to work as described. If I don't use any hot water for
about 4 hours though the water level in the feeder tank has reached the
overflow and starts trickling out. It's a tiny, tiny trickle, so much so
that the water doesn't pour out of the end of overflow pipe but trickles
out the end, back along the bottom and is absorbed by the wall. The
plaster on that wall is blown. :-(

Thanks for all of the replys to the original post. Having done some
experimenting I've done/found the following out:

- the level at which the float valve cuts off is about 3 inches below
the overflow pipe.

- the feeder tank fills up irrespective of whether the cold water feed
is turned on or off. ie Overnight wednesday it filled up with the
stopcock for the cold water feed turned on. Last night it did the same
with the cold water feed turned off.

- the water in the feeder tank is lukewarm. Not boiling hot, but
slightly warm to the touch.

- there's no water coming from the steam vent pipe.

- there are no hot taps or pipes above the level of the tank.

Does anyone have any further ideas as to what may be happening/what I
can try before I call out a plumber?

Cheers,

Andrew

In an earlier contribution to this discussion,
Andrew L com wrote:

Andrew L wrote:
I've got a cylinder tank in the airing cupboard which has above it
two square tanks, one large one small. I believe the larger is
called the feeder tank. As hot water is drained from the cylinder
tank water is drained from the feeder tank into they cylinder, which
in turn is filled up from the cold water mains supply up until a
certain level (about a
1.5 inches below the overflow) at which point the float valve closes.

This all seems to work as described. If I don't use any hot water for
about 4 hours though the water level in the feeder tank has reached
the overflow and starts trickling out. It's a tiny, tiny trickle, so
much so that the water doesn't pour out of the end of overflow pipe
but trickles out the end, back along the bottom and is absorbed by
the wall. The plaster on that wall is blown. :-(

Thanks for all of the replys to the original post. Having done some
experimenting I've done/found the following out:

- the level at which the float valve cuts off is about 3 inches below
the overflow pipe.

- the feeder tank fills up irrespective of whether the cold water feed
is turned on or off. ie Overnight wednesday it filled up with the
stopcock for the cold water feed turned on. Last night it did the same
with the cold water feed turned off.

- the water in the feeder tank is lukewarm. Not boiling hot, but
slightly warm to the touch.

- there's no water coming from the steam vent pipe.

- there are no hot taps or pipes above the level of the tank.

Does anyone have any further ideas as to what may be happening/what I
can try before I call out a plumber?

Cheers,

Andrew

Is the water level in the small tank higher than that in the large one? [The
small tank is the fill & expansion tank for the heating/hot water primary
circuit]

The water in the primary circuit is heated by the boiler, and is pumped
through a coil inside your hot water cylinder - enabling it to heat the
domestic hot water without mixing with it. However, if that coil develops a
leak, the waters *do* mix - and water flows from one circuit to the other.
The direction of flow is determined by the relative pressures in the
circuits. Whichever circuit has a higher water level in its header tank is
at a slightly higher pressure than the other one - and water flows from high
to low pressure.

If your cold header tank continues to fill with the water supply turned off
then - discounting a small rise due to expansion - the water *can* only be
coming from the other circuit. The fact that the water in the cold header is
lukewarm re-inforces the notion that it is coming from the primary circuit.

You say that when it reaches overflow level, the drip rate is very slow.
Could it be that the overflow level in the big tank is only *just* below the
static level in the small tank. If so, the pressures would be very nearly
equal by the time it rose to this level.

If this *is* your problem, you'll need a new hot water cylinder!
--
Cheers,
Set Square
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"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Andrew L com wrote:

Andrew L wrote:
I've got a cylinder tank in the airing cupboard which has above it
two square tanks, one large one small. I believe the larger is
called the feeder tank. As hot water is drained from the cylinder
tank water is drained from the feeder tank into they cylinder, which
in turn is filled up from the cold water mains supply up until a
certain level (about a
1.5 inches below the overflow) at which point the float valve closes.

This all seems to work as described. If I don't use any hot water for
about 4 hours though the water level in the feeder tank has reached
the overflow and starts trickling out. It's a tiny, tiny trickle, so
much so that the water doesn't pour out of the end of overflow pipe
but trickles out the end, back along the bottom and is absorbed by
the wall. The plaster on that wall is blown. :-(

Thanks for all of the replys to the original post. Having done some
experimenting I've done/found the following out:

- the level at which the float valve cuts off is about 3 inches below
the overflow pipe.

- the feeder tank fills up irrespective of whether the cold water feed
is turned on or off. ie Overnight wednesday it filled up with the
stopcock for the cold water feed turned on. Last night it did the same
with the cold water feed turned off.

- the water in the feeder tank is lukewarm. Not boiling hot, but
slightly warm to the touch.

- there's no water coming from the steam vent pipe.

- there are no hot taps or pipes above the level of the tank.

Does anyone have any further ideas as to what may be happening/what I
can try before I call out a plumber?

Cheers,

Andrew

Is the water level in the small tank higher than that in the large one?
[The
small tank is the fill & expansion tank for the heating/hot water primary
circuit]

The water in the primary circuit is heated by the boiler, and is pumped
through a coil inside your hot water cylinder - enabling it to heat the
domestic hot water without mixing with it. However, if that coil develops
a
leak, the waters *do* mix - and water flows from one circuit to the other.
The direction of flow is determined by the relative pressures in the
circuits. Whichever circuit has a higher water level in its header tank is
at a slightly higher pressure than the other one - and water flows from
high
to low pressure.

If your cold header tank continues to fill with the water supply turned
off
then - discounting a small rise due to expansion - the water *can* only be
coming from the other circuit. The fact that the water in the cold header
is
lukewarm re-inforces the notion that it is coming from the primary
circuit.

You say that when it reaches overflow level, the drip rate is very slow.
Could it be that the overflow level in the big tank is only *just* below
the
static level in the small tank. If so, the pressures would be very nearly
equal by the time it rose to this level.

If this *is* your problem, you'll need a new hot water cylinder!
--

One other possibility comes to mind - is there a leak between a cold mains
fed input and the hot water service via a defective mixer tap or temperature
control mixing valve located anywhere in the house?
Try turning off the cold water main at the stop tap and observe the header
or feeder tank as you call it.

Set Square wrote:
Is the water level in the small tank higher than that in the large one? [The
small tank is the fill & expansion tank for the heating/hot water primary
circuit]

Thanks Set Square,

No the water level (and overflow) of the small tank is below the water
level of the larger tank.

Cheers,

Andrew

In an earlier contribution to this discussion,
Andrew L com wrote:

Set Square wrote:
Is the water level in the small tank higher than that in the large
one? [The small tank is the fill & expansion tank for the
heating/hot water primary circuit]

Thanks Set Square,

No the water level (and overflow) of the small tank is below the water
level of the larger tank.

Cheers,

Andrew

And it's the larger tank which continues to fill, and overflows - even with
the water supply turned off?

Then I'm flummoxed!

The suggestion made by someone regarding some sort of cross-coupling between
the mains cold water system and low pressure hot water system seems worthy
of investigation.
--
Cheers,
Set Square
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Set Square wrote:
And it's the larger tank which continues to fill, and overflows - even with
the water supply turned off?

Then I'm flummoxed!

The suggestion made by someone regarding some sort of cross-coupling between
the mains cold water system and low pressure hot water system seems worthy
of investigation.

Downstairs we have a gravity fed mixer shower. Water comes direct from
the hot water tank into one side, and from the mains feed into another.
The temperature control is separate from the on-off control. Normally we
keep the temparature near maximum hot. Overnight last night as a test I
set it to cold...and this morning the level in the feeder tank hadn't
risen a millimetre.

This looks like it could be my chief suspect although quite exactly what
is happening I'm not sure.

Thanks,

Andrew

Set Square wrote:
And it's the larger tank which continues to fill, and overflows - even with
the water supply turned off?

Then I'm flummoxed!

The suggestion made by someone regarding some sort of cross-coupling between
the mains cold water system and low pressure hot water system seems worthy
of investigation.

Downstairs we have a gravity fed mixer shower. Water comes direct from
the hot water tank into one side, and from the mains feed into another.
The temperature control is separate from the on-off control. Normally we
keep the temparature near maximum hot. Overnight last night as a test I
set it to cold...and this morning the level in the feeder tank hadn't
risen a millimetre.

This looks like it could be my chief suspect although quite exactly what
is happening I'm not sure.

Thanks,

Andrew

In an earlier contribution to this discussion,
Andrew L com wrote:

Set Square wrote:
And it's the larger tank which continues to fill, and overflows -
even with the water supply turned off?

Then I'm flummoxed!

The suggestion made by someone regarding some sort of cross-coupling
between the mains cold water system and low pressure hot water
system seems worthy of investigation.

Downstairs we have a gravity fed mixer shower. Water comes direct from
the hot water tank into one side, and from the mains feed into
another. The temperature control is separate from the on-off control.
Normally we keep the temparature near maximum hot. Overnight last
night as a test I set it to cold...and this morning the level in the
feeder tank hadn't risen a millimetre.

This looks like it could be my chief suspect although quite exactly
what is happening I'm not sure.

Thanks,

Andrew

It does indeed! It sounds as if somehow, even with the shower turned off
(with nothing coming out of the shower-head), high pressure cold water can
flow across to the hot water side - and push hot water back up into the
header tank.

I guess that the mixer valve wasn't designed to cope with unequal hot and
cold pressures - and does the mixing *upstream* of the on/off valve.
--
Cheers,
Set Square
______
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Set Square wrote:
In an earlier contribution to this discussion,
Andrew L com wrote:


Set Square wrote:

And it's the larger tank which continues to fill, and overflows -
even with the water supply turned off?

Then I'm flummoxed!

The suggestion made by someone regarding some sort of cross-coupling
between the mains cold water system and low pressure hot water
system seems worthy of investigation.

Downstairs we have a gravity fed mixer shower. Water comes direct from
the hot water tank into one side, and from the mains feed into
another. The temperature control is separate from the on-off control.
Normally we keep the temparature near maximum hot. Overnight last
night as a test I set it to cold...and this morning the level in the
feeder tank hadn't risen a millimetre.

This looks like it could be my chief suspect although quite exactly
what is happening I'm not sure.

Thanks,

Andrew


It does indeed! It sounds as if somehow, even with the shower turned off
(with nothing coming out of the shower-head), high pressure cold water can
flow across to the hot water side - and push hot water back up into the
header tank.

I guess that the mixer valve wasn't designed to cope with unequal hot and
cold pressures - and does the mixing *upstream* of the on/off valve.

The hot and cold feeds go into a mixer tap (the temperature control) and
then to the shower head via an on/off tap. When the shower is switched
off it's almost impossible to turn the temperature control from hot
towards control - it's as if you're fighting a great pressure.

It's been operational for nearly two years and not caused a problem
before. However the water is exceptionally hard around here (it's
destroyed a dishwasher in four years) so I guess that there may be some
corrosion in there somewhere. Keeping the temperature tap on cold is at
least a temporary fix.

Many thanks to all who offered advice.

Cheers,

Andrew

In an earlier contribution to this discussion,
Andrew L com wrote:


The hot and cold feeds go into a mixer tap (the temperature control)
and then to the shower head via an on/off tap. When the shower is
switched off it's almost impossible to turn the temperature control
from hot towards control - it's as if you're fighting a great
pressure.

It's been operational for nearly two years and not caused a problem
before. However the water is exceptionally hard around here (it's
destroyed a dishwasher in four years) so I guess that there may be
some corrosion in there somewhere. Keeping the temperature tap on
cold is at least a temporary fix.

Many thanks to all who offered advice.

Cheers,

Andrew


Well, I'm glad that you didn't replace your hot cylinder unnecessarily!
--
Cheers,
Set Square
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