Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water? What effect could this
have on the sytem if this is wrong as I suspect?

TIA

Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water?

It should be above the water level to create an air gap.

What effect could this
have on the sytem if this is wrong as I suspect?

Someone will be along soon....


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

"The Medway Handyman" wrote in message
...
Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water?

It should be above the water level to create an air gap.

What effect could this
have on the sytem if this is wrong as I suspect?

Someone will be along soon....


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

This pipe is also an open vent pipe, and should not be blocked in any way.

The Medway Handyman wrote:

Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water?

It should be above the water level to create an air gap.

Why does it need an air gap?

On Nov 21, 5:38*pm, Ronald Raygun
wrote:
The Medway Handyman wrote:
Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water?

It should be above the water level to create an air gap.

Why does it need an air gap?

To prevent circulation of water through it. (Convection or pump).

Ronald Raygun wrote:
The Medway Handyman wrote:

Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong
and it should end above the level of the water?

It should be above the water level to create an air gap.

Why does it need an air gap?

AFAIK when water is heated it expands & any excess overflows into the tank
via the pipe. When the system cools the water contracts IYSWIM. If the
pipe is below the surface, water could be sucked back into the system, which
would cause the tank to overflow.


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

The Medway Handyman wrote:

Ronald Raygun wrote:
The Medway Handyman wrote:

Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong
and it should end above the level of the water?

It should be above the water level to create an air gap.

Why does it need an air gap?

AFAIK when water is heated it expands & any excess overflows into the tank
via the pipe.

Yes.

When the system cools the water contracts IYSWIM.

Yes.

If the
pipe is below the surface, water could be sucked back into the system,

Yes.

which would cause the tank to overflow.

No it wouldn't, unless there's something I'm missing, in which case
plase explain.

The tank obviously can't overflow as a result of sucking water out of it,
but of course what could happen is, if it sucked out enough to cause
the float to drop and to open the top-up valve, then too much new water
would be added to the system. But this shouldn't happen because the float
valve would already have been shut before the water heated up and expanded.

Therefore any water spewed into the tank (with or without an air gap)
would raise the level, causing the float to apply even more force on
the top-up valve to keep it shut.

If the same quantity of water is then sucked back out of the tank, it will
cause the tank level to drop only to its previous level, which is not low
enough to open the top-up valve.

Ronald Raygun wrote:
The Medway Handyman wrote:

Ronald Raygun wrote:
The Medway Handyman wrote:

Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong
and it should end above the level of the water?

It should be above the water level to create an air gap.

Why does it need an air gap?

AFAIK when water is heated it expands & any excess overflows into
the tank via the pipe.

Yes.

When the system cools the water contracts IYSWIM.

Yes.

If the
pipe is below the surface, water could be sucked back into the
system,

Yes.

which would cause the tank to overflow.

No it wouldn't, unless there's something I'm missing, in which case
plase explain.

The tank obviously can't overflow as a result of sucking water out of
it, but of course what could happen is, if it sucked out enough to
cause
the float to drop and to open the top-up valve, then too much new
water would be added to the system. But this shouldn't happen
because the float valve would already have been shut before the water
heated up and expanded.

Its only a theory :-)

Assuming the system is hot & the float is 'up' - the expansion pipe then
falls into the tank. As the system cools, water would be sucked out, so the
float drops & the tank fills back to the normal level. Then when the system
heats up the water expands & returns to the tank - which is already full -
so it overflows.

Can't see any other reason for an air gap?


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

On Nov 21, 12:02*pm, Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water? *What effect could this
have on the sytem if this is wrong as I suspect?

TIA

In a traditional heating system there should be a 5 gallon header
tank, there should be four or five inches of water in it. The
expansion pipe should not dip into it, the end of the pipe should be
an inch or two below the top of the tank.
If it does, it indicates the ball/float valve in you tank needs
adjusting or a new washer. Or the system is/was pumping over, ie is
incorrectly designed and the circulation pump is sending water up the
expansion pipe into the tank. If so, this needs seeing to. Or the
heat exchanger in your cylinder has a leak.
You need to check if water is coming from the tank overflow and if
so, all the time or just when the pump is running.

On Sun, 21 Nov 2010 10:44:59 -0800 (PST), harry
wrote:

On Nov 21, 12:02*pm, Jack wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water? *What effect could this
have on the sytem if this is wrong as I suspect?

TIA

In a traditional heating system there should be a 5 gallon header
tank, there should be four or five inches of water in it. The
expansion pipe should not dip into it, the end of the pipe should be
an inch or two below the top of the tank.
If it does, it indicates the ball/float valve in you tank needs
adjusting or a new washer. Or the system is/was pumping over, ie is
incorrectly designed and the circulation pump is sending water up the
expansion pipe into the tank. If so, this needs seeing to. Or the
heat exchanger in your cylinder has a leak.
You need to check if water is coming from the tank overflow and if
so, all the time or just when the pump is running.

Thanks for all the replies. Regarding the pipe being under the water
- the prat who did the original fitting made the pipe so long it
nearly touched the bottom of the tank. I shall be giving a good look
at the rest of his work. Thanks for the tips.

On 21/11/10 19:49, Jack wrote:
On Sun, 21 Nov 2010 10:44:59 -0800 (PST),
wrote:

On Nov 21, 12:02 pm, wrote:
Morning,

Had reason to look at this and found the expansion pipe went down
under the water in the tank - am I right in thinking this is wrong and
it should end above the level of the water? What effect could this
have on the sytem if this is wrong as I suspect?

TIA

In a traditional heating system there should be a 5 gallon header
tank, there should be four or five inches of water in it. The
expansion pipe should not dip into it, the end of the pipe should be
an inch or two below the top of the tank.
If it does, it indicates the ball/float valve in you tank needs
adjusting or a new washer. Or the system is/was pumping over, ie is
incorrectly designed and the circulation pump is sending water up the
expansion pipe into the tank. If so, this needs seeing to. Or the
heat exchanger in your cylinder has a leak.
You need to check if water is coming from the tank overflow and if
so, all the time or just when the pump is running.

Thanks for all the replies. Regarding the pipe being under the water
- the prat who did the original fitting made the pipe so long it
nearly touched the bottom of the tank. I shall be giving a good look
at the rest of his work. Thanks for the tips.
Is it a tradiional heating system?
Diagram please (with many clours for clarification)
[g]