I've just done most of the pipework up to
the new combi.  There is just the connections to
the unit to complete.
Do I just use elbows to make that tight turn to meet
the combi connections?

Also, I haven't done the gas supply pipework yet so
this pipe would have to leapfrog a horizontal section of
the mains supply to the unit.  Is this acceptable?

Thanks.

Arthur

In article <d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com>, Arthur
 writes

>I've just done most of the pipework up to
>the new combi.  There is just the connections to
>the unit to complete.
>Do I just use elbows to make that tight turn to meet
>the combi connections?
>
>Also, I haven't done the gas supply pipework yet so
>this pipe would have to leapfrog a horizontal section of
>the mains supply to the unit.  Is this acceptable?


System connections (the big stuff), swept bends essential.
Feed & h/w connections swept bends recommended.
ie. not elbows.

Prob not what you wanted to hear . . . 
-- 
fred

fred wrote:

> In article <d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com>, Arthur
>  writes
> 
>>I've just done most of the pipework up to
>>the new combi.  There is just the connections to
>>the unit to complete.
>>Do I just use elbows to make that tight turn to meet
>>the combi connections?
>>
>>Also, I haven't done the gas supply pipework yet so
>>this pipe would have to leapfrog a horizontal section of
>>the mains supply to the unit.  Is this acceptable?
> 
> 
> System connections (the big stuff), swept bends essential.
> Feed & h/w connections swept bends recommended.
> ie. not elbows.
> 
> Prob not what you wanted to hear . . . 


Thanks.

The pipework I've done so far is still shy of the combi by a foot or so.
What are these system connections you mention?
Do you have a link?

Arthur

In article <d6n21i$oj4$1@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com>, Arthur
 writes

>fred wrote:
>> In article <d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com>, Arthur
>>  writes
>> 
>>>I've just done most of the pipework up to
>>>the new combi.  There is just the connections to
>>>the unit to complete.
>>>Do I just use elbows to make that tight turn to meet
>>>the combi connections?
>>>
>>>Also, I haven't done the gas supply pipework yet so
>>>this pipe would have to leapfrog a horizontal section of
>>>the mains supply to the unit.  Is this acceptable?
>> 
>> System connections (the big stuff), swept bends essential.
>> Feed & h/w connections swept bends recommended.
>> ie. not elbows.
>> 
>> Prob not what you wanted to hear . . . 
>
>Thanks.
>
>The pipework I've done so far is still shy of the combi by a foot or so.
>What are these system connections you mention?
>Do you have a link?


The system connections are the ones to and from your central heating
loop, probably 22mm, possibly 28mm. 22mm is right on the limit for
passing enough water to distribute the heat from the typical domestic
boiler so it is not a good idea to restrict the flow with the use of elbows
before the distribution tree starts to split off to different parts of the house.
Better to create bends from straight pipe using a pipe bender giving a
smooth radius to the bend of about 80mm.

Cold feed and hot output can be 15mm as hot water generating capabilities
of combis are limited but again swept bends mean less restriction and less
noise.

Regarding your last question on the gas supply, you shouldn't really need
to create a tightly bent rats nest of pipework, subtle return bends in your
CH/HW & gas pipework should allow pipes to pass in opposite directions
without this happening. Try not to fit one set of pipes then force others to fit
around them, design the layout of the pipes on paper before hand, it
worked for me.

For more info, have a look at the heating section our very own faq:
http://www.diyfaq.org.uk/contents.html
-- 
fred

"Arthur"  wrote in message
news:d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...

> I've just done most of the pipework up to
> the new combi.  There is just the connections to
> the unit to complete.
> Do I just use elbows to make that tight turn to meet
> the combi connections?
>
> Also, I haven't done the gas supply pipework yet so
> this pipe would have to leapfrog a horizontal section of
> the mains supply to the unit.  Is this acceptable?
>
> Thanks.
>
> Arthur


- Change the stop cock to a "full bore" stop-cock.

- Make sure the combi has a dedicated, preferably 22mm, cold water inlet
pipe right back to the main stop cock, even if the mains is only 15mm.

- Do not tee cold supplies off this pipe.

- Take the hot supply of the shower right back to the combi outlet.

- The cold to the shower: have teed off the cold water inlet to the combi,
just before the combi.  This should be the "only" cold water pipe teed off
this pipe.  This is so when there is pressure fluctuations around the combi
the hot and cold to the shower are influenced at about the same rate.

- The shower is the most important outlet in a water system,  All must be
geared to ensure constant pressure and volume to the mixers.

- use bends where possible and elbows when there is no alternative.

If you have not done this I strongly advise you to do it while you at this
stage.


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"Doctor Evil"  wrote in message 
news:428f1cc4@news.usenetzone.com...

>
> "Arthur"  wrote in message
> news:d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...
>> I've just done most of the pipework up to
>> the new combi.  There is just the connections to
>> the unit to complete.
>> Do I just use elbows to make that tight turn to meet
>> the combi connections?
>>
>> Also, I haven't done the gas supply pipework yet so
>> this pipe would have to leapfrog a horizontal section of
>> the mains supply to the unit.  Is this acceptable?
>>
>> Thanks.
>>
>> Arthur
>
> - Change the stop cock to a "full bore" stop-cock.
>

If you are going to change your stop cock, make sure you fit one that 
conforms to regulations, as fitting a non approved one could lead to 
prosecution by the water authorities. IIRC a stop cock BS1010 with a loose 
jumper must be fitted as it acts as a non return to prevent any 
contamination getting back into the main.

"Kaiser"  wrote in message
news:428f24f9$0$295$cc9e4d1f@news-text.dial.pipex.com...

>
> "Doctor Evil"  wrote in message
> news:428f1cc4@news.usenetzone.com...
> >
> > "Arthur"  wrote in message
> > news:d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...
> >> I've just done most of the pipework up to
> >> the new combi.  There is just the connections to
> >> the unit to complete.
> >> Do I just use elbows to make that tight turn to meet
> >> the combi connections?
> >>
> >> Also, I haven't done the gas supply pipework yet so
> >> this pipe would have to leapfrog a horizontal section of
> >> the mains supply to the unit.  Is this acceptable?
> >>
> >> Thanks.
> >>
> >> Arthur
> >
> > - Change the stop cock to a "full bore" stop-cock.
> >
> If you are going to change your stop cock, make sure you fit one that
> conforms to regulations, as fitting a non approved one could lead to
> prosecution by the water authorities. IIRC a stop cock BS1010 with a loose
> jumper must be fitted as it acts as a non return to prevent any
> contamination getting back into the main.


Loose jumper?  Not so.  Many water companies are now installing full bore
valves lever valves.  Many charge around 70-80 to fit one.


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"Doctor Evil"  wrote in message 
news:428f3aad@news.usenetzone.com...

>
> "Kaiser"  wrote in message
> news:428f24f9$0$295$cc9e4d1f@news-text.dial.pipex.com...
>>
>> "Doctor Evil"  wrote in message
>> news:428f1cc4@news.usenetzone.com...
>> >
>> > "Arthur"  wrote in message
>> > news:d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...
>> >> I've just done most of the pipework up to
>> >> the new combi.  There is just the connections to
>> >> the unit to complete.
>> >> Do I just use elbows to make that tight turn to meet
>> >> the combi connections?
>> >>
>> >> Also, I haven't done the gas supply pipework yet so
>> >> this pipe would have to leapfrog a horizontal section of
>> >> the mains supply to the unit.  Is this acceptable?
>> >>
>> >> Thanks.
>> >>
>> >> Arthur
>> >
>> > - Change the stop cock to a "full bore" stop-cock.
>> >
>> If you are going to change your stop cock, make sure you fit one that
>> conforms to regulations, as fitting a non approved one could lead to
>> prosecution by the water authorities. IIRC a stop cock BS1010 with a 
>> loose
>> jumper must be fitted as it acts as a non return to prevent any
>> contamination getting back into the main.
>
> Loose jumper?  Not so.  Many water companies are now installing full bore
> valves lever valves.  Many charge around 70-80 to fit one.
>


If they fit a full bore valve (which still has to meet the required BS) they 
are also required to fit a double check valve to prevent backflow, which 
rather defeats the object.

The only advantage is that you are able to shut off the incoming supply 
easier when they aren't seized.

The disadvantage we find with full bore lever valves is that they need 
exercising more often, as they are prone to seizing in hard water areas. In 
fact I've got to replace a 50mm Boss full bore in an industrial unit next 
week for that very reason.

"Kaiser"  wrote in message
news:428f4be7$0$292$cc9e4d1f@news-text.dial.pipex.com...

>
> "Doctor Evil"  wrote in message
> news:428f3aad@news.usenetzone.com...
> >
> > "Kaiser"  wrote in message
> > news:428f24f9$0$295$cc9e4d1f@news-text.dial.pipex.com...
> >>
> >> "Doctor Evil"  wrote in message
> >> news:428f1cc4@news.usenetzone.com...
> >> >
> >> > "Arthur"  wrote in message
> >> > news:d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...
> >> >> I've just done most of the pipework up to
> >> >> the new combi.  There is just the connections to
> >> >> the unit to complete.
> >> >> Do I just use elbows to make that tight turn to meet
> >> >> the combi connections?
> >> >>
> >> >> Also, I haven't done the gas supply pipework yet so
> >> >> this pipe would have to leapfrog a horizontal section of
> >> >> the mains supply to the unit.  Is this acceptable?
> >> >>
> >> >> Thanks.
> >> >>
> >> >> Arthur
> >> >
> >> > - Change the stop cock to a "full bore" stop-cock.
> >> >
> >> If you are going to change your stop cock, make sure you fit one that
> >> conforms to regulations, as fitting a non approved one could lead to
> >> prosecution by the water authorities. IIRC a stop cock BS1010 with a
> >> loose
> >> jumper must be fitted as it acts as a non return to prevent any
> >> contamination getting back into the main.
> >
> > Loose jumper?  Not so.  Many water companies are now installing full
bore
> > valves lever valves.  Many charge around 70-80 to fit one.
>
> If they fit a full bore valve (which still has to meet the required BS)
they
> are also required to fit a double check valve to prevent backflow, which
> rather defeats the object.


A 15mm stock-cock can seriously reduce pressure and flow.  You can always
fit a larger sized double check valve to improve flow combined with full
bore valve.


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"Doctor Evil"  wrote in message 
news:429068a0@news.usenetzone.com...

>
> "Kaiser"  wrote in message
> news:428f4be7$0$292$cc9e4d1f@news-text.dial.pipex.com...
>>
>> "Doctor Evil"  wrote in message
>> news:428f3aad@news.usenetzone.com...
>> >
>> > "Kaiser"  wrote in message
>> > news:428f24f9$0$295$cc9e4d1f@news-text.dial.pipex.com...
>> >>
>> >> "Doctor Evil"  wrote in message
>> >> news:428f1cc4@news.usenetzone.com...
>> >> >
>> >> > "Arthur"  wrote in message
>> >> > news:d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...
>> >> >> I've just done most of the pipework up to
>> >> >> the new combi.  There is just the connections to
>> >> >> the unit to complete.
>> >> >> Do I just use elbows to make that tight turn to meet
>> >> >> the combi connections?
>> >> >>
>> >> >> Also, I haven't done the gas supply pipework yet so
>> >> >> this pipe would have to leapfrog a horizontal section of
>> >> >> the mains supply to the unit.  Is this acceptable?
>> >> >>
>> >> >> Thanks.
>> >> >>
>> >> >> Arthur
>> >> >
>> >> > - Change the stop cock to a "full bore" stop-cock.
>> >> >
>> >> If you are going to change your stop cock, make sure you fit one that
>> >> conforms to regulations, as fitting a non approved one could lead to
>> >> prosecution by the water authorities. IIRC a stop cock BS1010 with a
>> >> loose
>> >> jumper must be fitted as it acts as a non return to prevent any
>> >> contamination getting back into the main.
>> >
>> > Loose jumper?  Not so.  Many water companies are now installing full
> bore
>> > valves lever valves.  Many charge around 70-80 to fit one.
>>
>> If they fit a full bore valve (which still has to meet the required BS)
> they
>> are also required to fit a double check valve to prevent backflow, which
>> rather defeats the object.
>
> A 15mm stock-cock can seriously reduce pressure and flow.  You can always
> fit a larger sized double check valve to improve flow combined with full
> bore valve.
>

True, but is it worth the effort?

"Kaiser"  wrote in message
news:4290a0d0$0$288$cc9e4d1f@news-text.dial.pipex.com...

>
> "Doctor Evil"  wrote in message
> news:429068a0@news.usenetzone.com...
> >
> > "Kaiser"  wrote in message
> > news:428f4be7$0$292$cc9e4d1f@news-text.dial.pipex.com...
> >>
> >> "Doctor Evil"  wrote in message
> >> news:428f3aad@news.usenetzone.com...
> >> >
> >> > "Kaiser"  wrote in message
> >> > news:428f24f9$0$295$cc9e4d1f@news-text.dial.pipex.com...
> >> >>
> >> >> "Doctor Evil"  wrote in message
> >> >> news:428f1cc4@news.usenetzone.com...
> >> >> >
> >> >> > "Arthur"  wrote in message
> >> >> > news:d6mmsl$8vt$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com...
> >> >> >> I've just done most of the pipework up to
> >> >> >> the new combi.  There is just the connections to
> >> >> >> the unit to complete.
> >> >> >> Do I just use elbows to make that tight turn to meet
> >> >> >> the combi connections?
> >> >> >>
> >> >> >> Also, I haven't done the gas supply pipework yet so
> >> >> >> this pipe would have to leapfrog a horizontal section of
> >> >> >> the mains supply to the unit.  Is this acceptable?
> >> >> >>
> >> >> >> Thanks.
> >> >> >>
> >> >> >> Arthur
> >> >> >
> >> >> > - Change the stop cock to a "full bore" stop-cock.
> >> >> >
> >> >> If you are going to change your stop cock, make sure you fit one
that
> >> >> conforms to regulations, as fitting a non approved one could lead to
> >> >> prosecution by the water authorities. IIRC a stop cock BS1010 with a
> >> >> loose
> >> >> jumper must be fitted as it acts as a non return to prevent any
> >> >> contamination getting back into the main.
> >> >
> >> > Loose jumper?  Not so.  Many water companies are now installing full
> > bore
> >> > valves lever valves.  Many charge around 70-80 to fit one.
> >>
> >> If they fit a full bore valve (which still has to meet the required BS)
> > they
> >> are also required to fit a double check valve to prevent backflow,
which
> >> rather defeats the object.
> >
> > A 15mm stock-cock can seriously reduce pressure and flow.  You can
always
> > fit a larger sized double check valve to improve flow combined with full
> > bore valve.
> >
> True, but is it worth the effort?


Usually.  I did this on a relatives house and the flowrate went up from 14
l/min to 18 l/min.  The water companies don't want any water backfeeding in
the case of negative pressure.  In the vast majority of homes that have
outside stop-cocks with integral double check valves, washing machines with
integral check valves and air breaks, mixer taps with check valves and air
breaks on cisterns, there is no problem, even if there is backflow. Some
water companies take the worst cases example and regulate on that.

Many combis are allowed to expand through the combi and down the cold main
line. This is backfeeding, although only a small amount.  In this case a
normal free jumper in  stop cock will impede performance as it will prevent
expansion down the mains pipe.


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