15mm when first fixing house run of combi boiler

[Mgrant]

When first fixing a house to be run of a combi boiler with a 25mm mdpe cold feed. Is 15mm suffice to pipe up the cold water services within the house?

 

[wattsie1987]

Will be fine but I'd run 22mm until the tee that supplys the combi if you have a good flow rate it will help when showering or running a bath if the washing machine ect is used at the same time.

 

[ShaunCorbs]

depending on how big the house is 22 or if big house 28mm to boiler t off then 22mm into boiler

 

[AWheating]

its standard practice to run the cold in 22mm in small to med houses on new builds, normally 22mm with min 15mm branches to each bathroom/ kitchen/ cloaks etc....... make sure the supply to the combi is teed off the 22mm and if its an unvented then def 22mm or larger to cylinder cupboard.

your plumbing design drawings should have pipe sizes on really, stick to drawings so if the system does not work as required its not your fault.

 

[Mgrant]

its standard practice to run the cold in 22mm in small to med houses on new builds, normally 22mm with min 15mm branches to each bathroom/ kitchen/ cloaks etc....... make sure the supply to the combi is teed off the 22mm and if its an unvented then def 22mm or larger to cylinder cupboard.

your plumbing design drawings should have pipe sizes on really, stick to drawings so if the system does not work as required its not your fault.

Do most new builds have plumbing design drawings with pipe sizes and pipe runs? The drawings I have been given doesn't even have radiator positions.

 

[ShaunCorbs]

Do most new builds have plumbing design drawings with pipe sizes and pipe runs? The drawings I have been given doesn't even have radiator positions.

no your supposed to draw them one and then the client agrees the rad position

 

[AWheating]

Do most new builds have plumbing design drawings with pipe sizes and pipe runs? The drawings I have been given doesn't even have radiator positions.

how bigs the builder/site? most small plumbing companies or med/large house builders will try and get drawings done by boiler/rad manufacturer. Ideal do a good service for new builds with there spec on.

if its a small job/builder then you may not need to have drawings but get all positions agreed in writing/ on builders drawing. The next question is who is taking design liability? if you are deciding on pipe, rad sizes then make sure your 100% on them as it may cost you to change stuff later.

Common engineering judgement should be used, ask the builder for u values or size to building regs min values etc...... many builders will want to fit a combi even when there is a high hot water demand, recommend whats best, if the builder tells you what to fit then its his problem if its not good enough.

 

[Mgrant]

Run the cold in 22 but guessing the hot will all be 15mm as this is what pipe size comes off the boiler?

 

[REDSAW]

if the boiler, bath, kitchen within 5 meter and not too many bends, it wont matter!.

 

[Mgrant]

there's a bath and two showers on the system though

 

[REDSAW]

there's a bath and two showers on the system though

and perhaps only 2 living there?
bit like a dining table and 8 chairs in a semi lol

 

[AWheating]

Run the cold in 22 but guessing the hot will all be 15mm as this is what pipe size comes off the boiler?

the hot pipework size depends on what system your fitting and what its supplying, a normal combi will only give a limited flow rate and 15mm will be fine. Sometimes reducing to 10mm to basin's can be a good idea or even flow restrictors to help save water and even out flow rates.