Does anyone know whether cast iron downpipes (from gutters, not soil)
are measured on the internal or external diameter? I need to repalce a
short run, and bit I have is about 80mm external diameter (more or less,
accounting for the paint and rust), while all the CI pipe I find online
is 75mm, so I'm wondering whether I should be measuring the ID or
whether the new stuff is actually a different size. (Of course, it
would have been either 3" or 3 1/4" in the day.) Just to confuse the
issue, some suppliers have plastic pipe in 80mm, which may be a
cost-efective way forward (as 6' of CI seems to be £70-80!).

If it wasn't 20 feet plus up the wall and above the conservatory roof,
I'd rip it all down and replace with plastic, despite the historic
aspect, but that will have to wait until we have some scaffolding up for
the roof job, which will probably be next summer now. I don't much
fancy dismantling CI pipework off a ladder, given its weight and the
likely need for 'destructive dismantling'.

"GMM" GlMiMa-AT-yahoo.co.uk wrote in message
...
Does anyone know whether cast iron downpipes (from gutters, not soil) are
measured on the internal or external diameter? I need to repalce a short
run, and bit I have is about 80mm external diameter (more or less,
accounting for the paint and rust), while all the CI pipe I find online is
75mm, so I'm wondering whether I should be measuring the ID or whether the
new stuff is actually a different size. (Of course, it would have been
either 3" or 3 1/4" in the day.) Just to confuse the issue, some
suppliers have plastic pipe in 80mm, which may be a cost-efective way
forward (as 6' of CI seems to be £70-80!).

If it wasn't 20 feet plus up the wall and above the conservatory roof, I'd
rip it all down and replace with plastic, despite the historic aspect, but
that will have to wait until we have some scaffolding up for the roof job,
which will probably be next summer now. I don't much fancy dismantling CI
pipework off a ladder, given its weight and the likely need for
'destructive dismantling'.

In general in the UK all pipework (but not electrical conduit) is sized by
the nominal bore.
So 75mm pipe will have a bore of about 75mm but bigger outside. (Depending
on wall thickness)
It's nominal because it varies due to having to make the pipe fittings
interchangable even if the wall thickness vary.
The pipe fittings are often fixed size even if the wall thicknesses vary.
Thicker walls yherefore reduce bore size (though it's still referred to as
the same bore size.)

It's not 75mm it's 3". BTW
mm comes from the EUSSR frogs

harryagain wrote:

In general in the UK all pipework [...] is sized by the nominal
bore. mm comes from the EUSSR frogs

The frogs do tend to use myriad different sizes, e.g. for copper elbows
compare and contrast ...

http://toolstation.fr/shop/d110/sd2698/p39317
http://toolstation.com/shop/d20/sd2698/p86114

Surprised their unions haven't found a way to outlaw push-fit, try to
buy a "pince à emboiture" over here, they don't seem to make a 15mm
"matrix" for them ...

http://youtu.be/__X3K2EmPCQ

Andy Burns wrote:

try to buy a "pince à emboiture" over here, they don't seem to make a
15mm "matrix" for them ...

I take that back, the manufacturer does make a 15/22/28 set

http://rothenberger.com/en/products/...?article=12327

On 07/08/2014 06:47, harryagain wrote:
"GMM" GlMiMa-AT-yahoo.co.uk wrote in message
...
Does anyone know whether cast iron downpipes (from gutters, not soil) are
measured on the internal or external diameter? I need to repalce a short
run, and bit I have is about 80mm external diameter (more or less,
accounting for the paint and rust), while all the CI pipe I find online is
75mm, so I'm wondering whether I should be measuring the ID or whether the
new stuff is actually a different size. (Of course, it would have been
either 3" or 3 1/4" in the day.) Just to confuse the issue, some
suppliers have plastic pipe in 80mm, which may be a cost-efective way
forward (as 6' of CI seems to be £70-80!).

If it wasn't 20 feet plus up the wall and above the conservatory roof, I'd
rip it all down and replace with plastic, despite the historic aspect, but
that will have to wait until we have some scaffolding up for the roof job,
which will probably be next summer now. I don't much fancy dismantling CI
pipework off a ladder, given its weight and the likely need for
'destructive dismantling'.

In general in the UK all pipework (but not electrical conduit) is sized by
the nominal bore.
So 75mm pipe will have a bore of about 75mm but bigger outside. (Depending
on wall thickness)
It's nominal because it varies due to having to make the pipe fittings
interchangable even if the wall thickness vary.
The pipe fittings are often fixed size even if the wall thicknesses vary.
Thicker walls yherefore reduce bore size (though it's still referred to as
the same bore size.)

It's not 75mm it's 3". BTW
mm comes from the EUSSR frogs

While generally true for pipework based upon the original wrought iron
and cast iron pipe sizes, (i.e. today steel and plastic but not copper)
the problem is that 80mm OD does not correspond to any standard pipe.
2.5 inch bore is nominally 73mm OD, while 3 inch bore is nominally 89mm
OD. I suspect that, as rainwater pipes never needed to have a BSP thread
put on the outside, they don't comply with that general rule.


--
Colin Bignell

In article ,
Andy Burns writes:
harryagain wrote:

In general in the UK all pipework [...] is sized by the nominal
bore. mm comes from the EUSSR frogs

The frogs do tend to use myriad different sizes, e.g. for copper elbows
compare and contrast ...

http://toolstation.fr/shop/d110/sd2698/p39317
http://toolstation.com/shop/d20/sd2698/p86114

Although they call them something else, you will find their threaded
plumbing fittings are 1/2" BSP, 3/4" BSP, etc. This is useful for
buying thermostatic shower mixers, which are much cheaper in France
than they are here.

For copper tube, their equivalent of 15mm is 14mm, but unlike here,
many sizes are more commonly used too. (If you go to somewhere like
BES, you will find all the sizes here too, but you won't find them
in stock in a standard plumber's merchant.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 07/08/2014 08:12, Nightjar "cpb"@ insert my surname here wrote:
On 07/08/2014 06:47, harryagain wrote:
"GMM" GlMiMa-AT-yahoo.co.uk wrote in message
...
Does anyone know whether cast iron downpipes (from gutters, not soil)
are
measured on the internal or external diameter? I need to repalce a
short
run, and bit I have is about 80mm external diameter (more or less,
accounting for the paint and rust), while all the CI pipe I find
online is
75mm, so I'm wondering whether I should be measuring the ID or
whether the
new stuff is actually a different size. (Of course, it would have been
either 3" or 3 1/4" in the day.) Just to confuse the issue, some
suppliers have plastic pipe in 80mm, which may be a cost-efective way
forward (as 6' of CI seems to be £70-80!).

If it wasn't 20 feet plus up the wall and above the conservatory
roof, I'd
rip it all down and replace with plastic, despite the historic
aspect, but
that will have to wait until we have some scaffolding up for the roof
job,
which will probably be next summer now. I don't much fancy
dismantling CI
pipework off a ladder, given its weight and the likely need for
'destructive dismantling'.

In general in the UK all pipework (but not electrical conduit) is
sized by
the nominal bore.
So 75mm pipe will have a bore of about 75mm but bigger outside.
(Depending
on wall thickness)
It's nominal because it varies due to having to make the pipe fittings
interchangable even if the wall thickness vary.
The pipe fittings are often fixed size even if the wall thicknesses vary.
Thicker walls yherefore reduce bore size (though it's still referred
to as
the same bore size.)

It's not 75mm it's 3". BTW
mm comes from the EUSSR frogs

While generally true for pipework based upon the original wrought iron
and cast iron pipe sizes, (i.e. today steel and plastic but not copper)
the problem is that 80mm OD does not correspond to any standard pipe.
2.5 inch bore is nominally 73mm OD, while 3 inch bore is nominally 89mm
OD. I suspect that, as rainwater pipes never needed to have a BSP thread
put on the outside, they don't comply with that general rule.


Indeed, which is sort of my problem: Although they don't need a thread,
CI pipes are produced with a connector and wall bracket integral to one
end. If that doesn't accept the existing pipe, then it can't be
compatible, and that's 80 quid (and all the asociated trouble of
sourcing it) down the swanny, for one short length. What seems to be
difficult to establish is whether all these various sizes are similar
and compatible or whether they are all specific to individual
manufacturers, in which case everything needs changing (so I may as well
replace it with plastic).
If I assume a nominal wall thickness of 1/4 inch / 6mm (I don't hink
it's that much, but it's more than 1/8), then the 80mm OD becomes 68mm
ID, oddly the size of new plastic pipe.

On 07/08/2014 21:48, GMM wrote:
On 07/08/2014 08:12, Nightjar "cpb"@ insert my surname here wrote:
On 07/08/2014 06:47, harryagain wrote:
"GMM" GlMiMa-AT-yahoo.co.uk wrote in message
...
Does anyone know whether cast iron downpipes (from gutters, not soil)
are
measured on the internal or external diameter? I need to repalce a
short
run, and bit I have is about 80mm external diameter (more or less,
accounting for the paint and rust), while all the CI pipe I find
online is
75mm, so I'm wondering whether I should be measuring the ID or
whether the
new stuff is actually a different size. (Of course, it would have been
either 3" or 3 1/4" in the day.) Just to confuse the issue, some
suppliers have plastic pipe in 80mm, which may be a cost-efective way
forward (as 6' of CI seems to be £70-80!).

If it wasn't 20 feet plus up the wall and above the conservatory
roof, I'd
rip it all down and replace with plastic, despite the historic
aspect, but
that will have to wait until we have some scaffolding up for the roof
job,
which will probably be next summer now. I don't much fancy
dismantling CI
pipework off a ladder, given its weight and the likely need for
'destructive dismantling'.

In general in the UK all pipework (but not electrical conduit) is
sized by
the nominal bore.
So 75mm pipe will have a bore of about 75mm but bigger outside.
(Depending
on wall thickness)
It's nominal because it varies due to having to make the pipe fittings
interchangable even if the wall thickness vary.
The pipe fittings are often fixed size even if the wall thicknesses
vary.
Thicker walls yherefore reduce bore size (though it's still referred
to as
the same bore size.)

It's not 75mm it's 3". BTW
mm comes from the EUSSR frogs

While generally true for pipework based upon the original wrought iron
and cast iron pipe sizes, (i.e. today steel and plastic but not copper)
the problem is that 80mm OD does not correspond to any standard pipe.
2.5 inch bore is nominally 73mm OD, while 3 inch bore is nominally 89mm
OD. I suspect that, as rainwater pipes never needed to have a BSP thread
put on the outside, they don't comply with that general rule.


Indeed, which is sort of my problem: Although they don't need a thread,
CI pipes are produced with a connector and wall bracket integral to one
end. If that doesn't accept the existing pipe, then it can't be
compatible, and that's 80 quid (and all the asociated trouble of
sourcing it) down the swanny, for one short length. What seems to be
difficult to establish is whether all these various sizes are similar
and compatible or whether they are all specific to individual
manufacturers, in which case everything needs changing (so I may as well
replace it with plastic).
If I assume a nominal wall thickness of 1/4 inch / 6mm (I don't hink
it's that much, but it's more than 1/8), then the 80mm OD becomes 68mm
ID, oddly the size of new plastic pipe.

I don't like plastic rainwater goods. I much prefer cast aluminium, such
as Alumasc:

http://www.alumascrainwater.co.uk/

You could probably do worse than contact their technical support, say
you want to match an existing CI downpipe and ask them which of their
products is the right one.


--
Colin Bignell

From my experience of cast iron piping is that they are quite a sloppy fit in their connectors and slight differences in overall diameter are not going to be a problem. Getting hold of sections might be a bigger problem and I suspect you will have to source them from salvagers.

Richard

On 08/08/2014 00:32, Tricky Dicky wrote:
From my experience of cast iron piping is that they are quite a sloppy fit in their connectors and slight differences in overall diameter are not going to be a problem. Getting hold of sections might be a bigger problem and I suspect you will have to source them from salvagers.


You can buy cast iron rainwater goods at Jewsons.

--
Colin Bignell

You can buy cast iron rainwater goods at Jewsons.

I've been following this thread with interest,
as I have been vaguely thinking of installing a long downpipe -
around 50ft - and would probably be required to use cast-iron
as the property is a listed building,
and the downpipe would be in the front of the building.

I'm wondering if this would be a feasible project?

The reason I am considering this is that at present
the rain water from a very large roof goes over a valley
in the roof of our part of the property - an old orphanage -
and it is slightly disturbing to have what sounds like
quite a large river going over our heads.

--
Timothy Murphy
e-mail: gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin 2, Ireland

On 07/08/2014 22:56, Nightjar "cpb"@ insert my surname here wrote:

I don't like plastic rainwater goods. I much prefer cast aluminium, such
as Alumasc:

http://www.alumascrainwater.co.uk/

You could probably do worse than contact their technical support, say
you want to match an existing CI downpipe and ask them which of their
products is the right one.

I'd be cautious about aluminium in contact with iron. Make sure you have
a gap of some sort - a good thick coat of paint might do - to prevent
any funny galvanic stuff going on.

Andy

On 08/08/2014 10:14, Vir Campestris wrote:
On 07/08/2014 22:56, Nightjar "cpb"@ insert my surname here wrote:

I don't like plastic rainwater goods. I much prefer cast aluminium, such
as Alumasc:

http://www.alumascrainwater.co.uk/

You could probably do worse than contact their technical support, say
you want to match an existing CI downpipe and ask them which of their
products is the right one.

I'd be cautious about aluminium in contact with iron. Make sure you have
a gap of some sort - a good thick coat of paint might do - to prevent
any funny galvanic stuff going on.

They recommend a thick layer of bitumen, but I was thinking more of
simply asking their technical support about sizes.


--
Colin Bignell

On 08/08/2014 10:12, Timothy Murphy wrote:

You can buy cast iron rainwater goods at Jewsons.

I've been following this thread with interest,
as I have been vaguely thinking of installing a long downpipe -
around 50ft - and would probably be required to use cast-iron
as the property is a listed building,
and the downpipe would be in the front of the building.

Cast aluminium, which is available as visually the same, would probably
be accepted, unless it is Grade I.

I'm wondering if this would be a feasible project?

The reason I am considering this is that at present
the rain water from a very large roof goes over a valley
in the roof of our part of the property - an old orphanage -
and it is slightly disturbing to have what sounds like
quite a large river going over our heads.

Has it caused problems? If not, I would be inclined to leave it as it is.


--
Colin Bignell

Nightjar wrote:

I've been following this thread with interest,
as I have been vaguely thinking of installing a long downpipe -
around 50ft - and would probably be required to use cast-iron
as the property is a listed building,
and the downpipe would be in the front of the building.

The reason I am considering this is that at present
the rain water from a very large roof goes over a valley
in the roof of our part of the property - an old orphanage -
and it is slightly disturbing to have what sounds like
quite a large river going over our heads.

Has it caused problems? If not, I would be inclined to leave it as it is.

Thanks for your helpful response.

The roof leaks slightly under very heavy rain.
The quantity of water that goes over the roof is astonishing.
This is a very large building - we only live in a small part of it -
and all the rain falling on the roof goes over our valley.

Our builder offered to put in a downpipe some time ago,
but when he came with a colleague to look at it
they decided the quantity of water falling
was too great for a soak in the front of the house.
I wanted to collect the water in a tank/cistern,
but they decreed that this was impractical.



--
Timothy Murphy
e-mail: gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin 2, Ireland

I don't know if this info will be any use to anyone, but the new cast
iron that my son is putting up is approx 70mm inside dia and 80mm
outside. The other end has the mounting and larger dia for the next
section to fit into.

I meant to take a micrometer, but forgot so just measured with a rule.

He has 2 of these pipes that take water from a large roof in the next
garden down a sandstone wall into a soakaway.

His brother and a friend came to help him last weekend. They spent 4
hours setting up the scaffolding tower and inserting wooden plugs into
the soft sandstone, while he was "unfortunately" forced to take a long
and important business call. His brother was not very pleased. The pipes
are still lying on the ground, which is why I was able to measure.
--
Bill

On 08/08/2014 17:52, Bill wrote:
I don't know if this info will be any use to anyone, but the new cast
iron that my son is putting up is approx 70mm inside dia and 80mm
outside. The other end has the mounting and larger dia for the next
section to fit into.

I meant to take a micrometer, but forgot so just measured with a rule.

He has 2 of these pipes that take water from a large roof in the next
garden down a sandstone wall into a soakaway.

His brother and a friend came to help him last weekend. They spent 4
hours setting up the scaffolding tower and inserting wooden plugs into
the soft sandstone, while he was "unfortunately" forced to take a long
and important business call. His brother was not very pleased. The pipes
are still lying on the ground, which is why I was able to measure.

I suspect that what would be of most use to the OP would be to know what
size that was sold as.

--
Colin Bignell

On 08/08/2014 12:59, Timothy Murphy wrote:
Nightjar wrote:

I've been following this thread with interest,
as I have been vaguely thinking of installing a long downpipe -
around 50ft - and would probably be required to use cast-iron
as the property is a listed building,
and the downpipe would be in the front of the building.

The reason I am considering this is that at present
the rain water from a very large roof goes over a valley
in the roof of our part of the property - an old orphanage -
and it is slightly disturbing to have what sounds like
quite a large river going over our heads.

Has it caused problems? If not, I would be inclined to leave it as it is.

Thanks for your helpful response.

The roof leaks slightly under very heavy rain.

That sounds as though the gulley is filling up and spilling over the
edge of its lining, under the slates / tiles.

The quantity of water that goes over the roof is astonishing.
This is a very large building - we only live in a small part of it -
and all the rain falling on the roof goes over our valley.

Our builder offered to put in a downpipe some time ago,
but when he came with a colleague to look at it
they decided the quantity of water falling
was too great for a soak in the front of the house.
I wanted to collect the water in a tank/cistern,
but they decreed that this was impractical.

If there is not room for a soak away in front of the house, then there
is not much you can do, unless there is a surface water drain in the
area the water can be directed into. Soak aways need to be at least 5
metres from any building and of a size that can cope with the highest
water flow likely.

You might do better looking at whether the peak capacity of the gully
can be improved.


--
Colin Bignell

In message , "Nightjar
\"cpb\"@" "insert my surname writes
On 08/08/2014 17:52, Bill wrote:
I don't know if this info will be any use to anyone, but the new cast
iron that my son is putting up is approx 70mm inside dia and 80mm
outside. The other end has the mounting and larger dia for the next
section to fit into.

I meant to take a micrometer, but forgot so just measured with a rule.

He has 2 of these pipes that take water from a large roof in the next
garden down a sandstone wall into a soakaway.

His brother and a friend came to help him last weekend. They spent 4
hours setting up the scaffolding tower and inserting wooden plugs into
the soft sandstone, while he was "unfortunately" forced to take a long
and important business call. His brother was not very pleased. The pipes
are still lying on the ground, which is why I was able to measure.

I suspect that what would be of most use to the OP would be to know
what size that was sold as.

This is cut and pasted from an invoice. If I remember the micrometer, I
will take more measurements

2 of R3001E Primed Eared 75mm Cast Iron Downpipe x 1.83m length @ £99.70
10 of R0004 100mm Pipe Nails @ £4.10

Sub Total: £103.80

Delivery £0.00
VAT @ 20% £20.76
Total £124.56

If you have any questions about your order, please don't hesitate to
drop us an email at .

--
Bill

In message , Bill
writes
This is cut and pasted from an invoice. If I remember the micrometer, I
will take more measurements

2 of R3001E Primed Eared 75mm Cast Iron Downpipe x 1.83m length @
£99.70
10 of R0004 100mm Pipe Nails @ £4.10

OK, this pipe is 69.4 mm internal dia, 79.96 O/D. The larger socket end
into which the next section of pipe fits is 84.50 mm internal.

I also measured the old pipe from the wall, which we believe is the
original from approx 1890.

It is internal 66.5, external 77.85 and the larger socket end (and the
original cast hopper receiver 84.2 internal, all to include rust etc.
--
Bill

On 09/08/2014 11:36, Bill wrote:
In message , "Nightjar
\"cpb\"@" "insert my surname writes
On 08/08/2014 17:52, Bill wrote:
I don't know if this info will be any use to anyone, but the new cast
iron that my son is putting up is approx 70mm inside dia and 80mm
outside. The other end has the mounting and larger dia for the next
section to fit into.

I meant to take a micrometer, but forgot so just measured with a rule.

He has 2 of these pipes that take water from a large roof in the next
garden down a sandstone wall into a soakaway.

His brother and a friend came to help him last weekend. They spent 4
hours setting up the scaffolding tower and inserting wooden plugs into
the soft sandstone, while he was "unfortunately" forced to take a long
and important business call. His brother was not very pleased. The pipes
are still lying on the ground, which is why I was able to measure.

I suspect that what would be of most use to the OP would be to know
what size that was sold as.

This is cut and pasted from an invoice. If I remember the micrometer, I
will take more measurements

2 of R3001E Primed Eared 75mm Cast Iron Downpipe x 1.83m length @ £99.70
10 of R0004 100mm Pipe Nails @ £4.10

Sub Total: £103.80

Delivery £0.00
VAT @ 20% £20.76
Total £124.56

If you have any questions about your order, please don't hesitate to
drop us an email at .

Thanks Bill, that's very useful: It sounds like it's the same as mine
(80 OD, 70 ID), so if they call that 75mm, I know what I'm looking for.
The quoted size seems to be an average of the ID and OD (probably not,
just a convention of some sort), which is interesting. As you will
know, these have to be compatible to work together, with relatively
little scope for bodgery, given the way the socket is integral to the
pipe and the nature of cast iron. Unlike the plastic stuff, it's not a
cheap mistake to make, as you can see from your invoice (which is a very
good price from what I've seen).

On 09/08/2014 13:01, GMM wrote:
On 09/08/2014 11:36, Bill wrote:
In message , "Nightjar
\"cpb\"@" "insert my surname writes
On 08/08/2014 17:52, Bill wrote:
I don't know if this info will be any use to anyone, but the new cast
iron that my son is putting up is approx 70mm inside dia and 80mm
outside. The other end has the mounting and larger dia for the next
section to fit into.

I meant to take a micrometer, but forgot so just measured with a rule.

He has 2 of these pipes that take water from a large roof in the next
garden down a sandstone wall into a soakaway.

His brother and a friend came to help him last weekend. They spent 4
hours setting up the scaffolding tower and inserting wooden plugs into
the soft sandstone, while he was "unfortunately" forced to take a long
and important business call. His brother was not very pleased. The
pipes
are still lying on the ground, which is why I was able to measure.

I suspect that what would be of most use to the OP would be to know
what size that was sold as.

This is cut and pasted from an invoice. If I remember the micrometer, I
will take more measurements

2 of R3001E Primed Eared 75mm Cast Iron Downpipe x 1.83m length @ £99.70
10 of R0004 100mm Pipe Nails @ £4.10

Sub Total: £103.80

Delivery £0.00
VAT @ 20% £20.76
Total £124.56

If you have any questions about your order, please don't hesitate to
drop us an email at .

Thanks Bill, that's very useful: It sounds like it's the same as mine
(80 OD, 70 ID), so if they call that 75mm, I know what I'm looking for.
The quoted size seems to be an average of the ID and OD (probably not,
just a convention of some sort), which is interesting. As you will
know, these have to be compatible to work together, with relatively
little scope for bodgery, given the way the socket is integral to the
pipe and the nature of cast iron. Unlike the plastic stuff, it's not a
cheap mistake to make, as you can see from your invoice (which is a very
good price from what I've seen).


That is consistent with the sizes in this document (Page 120)

http://www.alumascrainwater.co.uk/pdf/Apex_cast.pdf

Nominal size 75mm, ID 70mm, OD 82.5mm Socket ID 90mm

I'm not quite sure how they make a 70mm bore with 3mm thick walls equal
an OD of 82.5mm though.


--
Colin Bignell