The opportunity has arisen to build a small single-storey flat-roofed
extension to my sixties bungalow: in effect, a long narrow room stretching
for about half the length of one exterior wall. The wall in question is
windowless and the main room behind it is the kitchen.

At the moment, kitchen waste water empties into an open gulley hard up
against the wall. Also, the boiler vent is located on the same wall, as is
an open-ended vertical 15mm copper pipe also connected to the boiler, the
purpose of which I don't know. Near the foot of the wall are two drain
cocks for the central heating system.

If the extension goes ahead, all of these will have to be relocated or
re-routed: the effect will essentially be the same as moving key parts of
the kitchen from an external wall to an internal one.

I'm hoping that the kitchen waste pipework can be run beneath the floor of
the extension to a newly-installed open drainage point against what will be
the new external wall, since the internal floor level is sufficiently high
to allow a generous fall. The drainage cocks can be moved to another part
of the system away from the extension, but what about the boiler? The vent
can perhaps be given a 90 degree bend upwards through the extension roof,
but what about that 15mm boiler-pipe? Is it a safety feature of some kind?
And are there any other problems about (in effect) moving a boiler from an
outside wall to an internal one?

Many thanks.

Sorry, I should have said that the boiler is not a condensing model.

In article ,
"Bert Coules" writes:
Sorry, I should have said that the boiler is not a condensing model.

I suspect you won't be able to find anyone willing to move it, without
replacing it with one to current regs (condensing). In the whole
scheme of things (building extension and moving the boiler pipework),
the additional cost of a new boiler isn't going to be very significant.

The open pipe is to release excess pressure if something goes wrong
and the water boils. (More commonly, it releases excess pressure if
the system is topped up after the pressure vessel has failed.)

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

Andrew Gabriel wrote:

I suspect you won't be able to find anyone willing to move it, without
replacing it with one to current regs (condensing).

Sorry, Andrew, I obviously didn't make myself clear. I don't want to move
the boiler: I was asking if it would be possible to reroute the mystery pipe
(which you've now identified for me - thanks) so that it still ended in the
open air albeit some distance away from its present termination point.

Could it, for example, be rotated through 180 degrees and go up through the
roof of the new extension instead of down? Would it still work effectively
like that if necessary?

On 24/06/2013 23:08, Bert Coules wrote:
Andrew Gabriel wrote:

I suspect you won't be able to find anyone willing to move it, without
replacing it with one to current regs (condensing).

Sorry, Andrew, I obviously didn't make myself clear. I don't want to
move the boiler: I was asking if it would be possible to reroute the
mystery pipe (which you've now identified for me - thanks) so that it
still ended in the open air albeit some distance away from its present
termination point.

Could it, for example, be rotated through 180 degrees and go up through
the roof of the new extension instead of down? Would it still work
effectively like that if necessary?


It needs to be able to self-drain, really, otherwise it could end up
with stagnant water sitting on the relief valve and possibly corroding
it stuck, or filling up with bacterial goo. Don't see why it shouldn't
drain into an indoor container which you can inspect. You just don't
want anyone getting sprayed with steam if it "lets go".

"newshound" wrote:

It needs to be able to self-drain, really...

I think I realised that just after I posted my question about inverting it.

Don't see why it shouldn't drain into an indoor container which you can
inspect. You just don't want anyone getting sprayed with steam if it "lets
go".

Good point. Would there be any disadvantage to making the pipe considerably
longer than it is at present? I'm wondering about a vertical drop to below
the floor level of the extension and then a falling gradient to the outside
of the opposite wall. Perhaps the internal diameter would have to be
increased to avoid a throttling effect (and the change in direction should
probably be a slow curve rather than a sharp angle for the same reason) but
apart from that it feels like it might be a workable solution.

Thanks for your reply.

In article ,
"Bert Coules" writes:
Andrew Gabriel wrote:

I suspect you won't be able to find anyone willing to move it, without
replacing it with one to current regs (condensing).

Sorry, Andrew, I obviously didn't make myself clear. I don't want to move
the boiler: I was asking if it would be possible to reroute the mystery pipe
(which you've now identified for me - thanks) so that it still ended in the
open air albeit some distance away from its present termination point.

Could it, for example, be rotated through 180 degrees and go up through the
roof of the new extension instead of down? Would it still work effectively
like that if necessary?

Download the installation instructions for your boiler and see if
fitting it away from an outside wall is allowed. Even if it is,
you would also have to find out if the appropriate flue extension
pieces are still available. These can be very expensive - sometimes
as much again as the boiler itself costs. Some condensing boilers
can use standard high quality (muPVC) drainpipe as flue extensions,
but a non-condensing boiler will require proprietary metal flue
extension pipework (much higher flue temperature), if the design
allows for extension pieces at all.

I suspect the installation instructions will require the pressure
relief pipework to terminate outdoors. In the worst failure case,
it could be ejecting 10's of kW of steam, and that could kill you
indoors.

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

Andrew, thanks for that, I'll do as you suggest. I've also been sketching
out an alternative plan for the extension which would avoid the problem
altogether, which might well prove to be the necessary solution.

On 25/06/2013 12:48, Andrew Gabriel wrote:
In article ,
"Bert Coules" writes:
Andrew Gabriel wrote:

I suspect you won't be able to find anyone willing to move it, without
replacing it with one to current regs (condensing).

Sorry, Andrew, I obviously didn't make myself clear. I don't want to move
the boiler: I was asking if it would be possible to reroute the mystery pipe
(which you've now identified for me - thanks) so that it still ended in the
open air albeit some distance away from its present termination point.

Could it, for example, be rotated through 180 degrees and go up through the
roof of the new extension instead of down? Would it still work effectively
like that if necessary?

Download the installation instructions for your boiler and see if
fitting it away from an outside wall is allowed. Even if it is,
you would also have to find out if the appropriate flue extension
pieces are still available. These can be very expensive - sometimes
as much again as the boiler itself costs. Some condensing boilers
can use standard high quality (muPVC) drainpipe as flue extensions,
but a non-condensing boiler will require proprietary metal flue
extension pipework (much higher flue temperature), if the design
allows for extension pieces at all.

I suspect the installation instructions will require the pressure
relief pipework to terminate outdoors. In the worst failure case,
it could be ejecting 10's of kW of steam, and that could kill you
indoors.

Agreed, although that would require multiple failures in the boiler
protection system. A bit like turning on a DHW tap just at the time when
a storage cylinder has become superheated. I was thinking about a
discharge behind a washing machine or dishwasher, or into an under-sink
cupboard which would give a bit of physical protection.

But I think Bert has a valid fix if he can divert under a floor and then
out, especially if he can go up to 22 mm.

On 24/06/2013 17:53, Bert Coules wrote:
Sorry, I should have said that the boiler is not a condensing model.

Might be pressure relief. Do you have a header tank?

Andy

Vir Campestris wrote:

Might be pressure relief.

Yes, according to Andrew Gabriel, that's exactly what it is.

Do you have a header tank?

No, it's a combi boiler. Thanks for your reply.

Bert Coules wrote:
The opportunity has arisen to build a small single-storey flat-roofed
extension to my sixties bungalow: in effect, a long narrow room
stretching for about half the length of one exterior wall. The wall
in question is windowless and the main room behind it is the kitchen.

At the moment, kitchen waste water empties into an open gulley hard up
against the wall. Also, the boiler vent is located on the same wall,
as is an open-ended vertical 15mm copper pipe also connected to the
boiler, the purpose of which I don't know. Near the foot of the wall
are two drain cocks for the central heating system.

If the extension goes ahead, all of these will have to be relocated or
re-routed: the effect will essentially be the same as moving key
parts of the kitchen from an external wall to an internal one.

I'm hoping that the kitchen waste pipework can be run beneath the
floor of the extension to a newly-installed open drainage point
against what will be the new external wall, since the internal floor
level is sufficiently high to allow a generous fall. The drainage
cocks can be moved to another part of the system away from the
extension, but what about the boiler? The vent can perhaps be given
a 90 degree bend upwards through the extension roof, but what about
that 15mm boiler-pipe? Is it a safety feature of some kind? And are
there any other problems about (in effect) moving a boiler from an
outside wall to an internal one?

I've just finished an extension just like this.
The flue pipe was extended upwards into the ceiling, thenat 90 degrees
across to an outside wall - we could have sent it straight upwards through
the roof but the wall was closer.
The blowoff pipe was extended about 6ft through a new exterior wall, clipped
to the wall it originally came out of and drylined and plastered over.
We also had the headache of the condensate, which was extended and plumbed
into an internal soil stack, all boxed in.

Your drains may need to be moved, that is, your underground drains may need
to be re-routed so that they aren't underneath the extension.

Phil L wrote:

I've just finished an extension just like this.

That's good to know, thanks. It's so valuable to hear from someone who's
carried out similar work.

Your drains may need to be moved...

Ironically, it's a drain that I put in myself when I bought the house and
relocated the kitchen that might be in the way. Why the devil didn't I
anticipate fifteen years ago what I would be planning to do today?