What Size Pipes To Run For HW From Megaflow To Bathroom, Etc

[nashville]

I have just bought a house that was partially renovated, before the previous owner became ill, so I am finishing half done jobs.

His plumber put in a new boiler and unvented cylinder, but there are no hw supply pipes to bathrooms or kitchen from cylinder.

1) The kitchen and one bathroom are at one end of the house. Do I run a 22mm pipe for hw from u/v cyl. to that end of house, then split to 15mm to bathroom and 15mm to kitchen, or will 15mm all the way be OK?

2) The other bathroom is on the other side of the house. Do I run a 22mm pipe all the way to the bathroom then reduce to 15mm for the split to basin/bath/shower, or will 15mm all the way be OK?

 

[Morris40]

run 22mm both ways as far as you can and only 15mm at the end, bath though 22mm upto bath

 

[rojaca]

if you what appliances are being fed someone may be good enough to do a quick pipesizing calc. depending on distance you may want to put in a secondary return pipe if necessary if the deadleg is too long to prevent unnecessary wastage of water

 

[Morris40]

you will not need a pipe sizing calc just run 22mm pipe as far as you can then finish in 15mm except for bath finsh in 22mm so ignore last post

 

[rojaca]

thats right. ignore the water regulations regarding wastage of water. Morris, off the top of your head do you know what the maximum permited deadleg for 22mm pipe is. Do you know how far the appliance are away? I suspect the answer is no to both.

 

[Morris40]

don't get your knickers in a twist, all i was saying was that a pipe sizing calc is not needed as you'd run 22mm, and i am a plumbing and heating engineer, i don't get time to read all the crap that WRAS come out with, i use my reading time to read Gas regs as this is far more important, i seem to have managed for the last 20 years

 

[barkie1]

do you know how a secondary return works? He would need to install a circulation pump which would mean energy usage! Also would need to run timed or on permantly. For the sake of 1 bathroom seems a bit pants. Bronze pump to conform to water reg's (fittings) and all the pipe needed for this MASSIVE run. Which will undoubtly be factored in to the amazing maths needed for a pipe calc. In short secondary return would not be reasonably practicable. They are usually installed in b and b's hotel's and houses with many bathrooms and en-suite's.

 

[Morris40]

I concur with Barkie1, rules and REGS are all well and good but in the real world things happen in a different way

 

[rojaca]

...and large domestic properties.

Fair enough. reading the post again it does only indicate that there are only two bathrooms and a kitchen. So yes going for pumped secondary circ would be way over the top.

A quick look at the loading units for the hot to a normal kitchen and bathroom based on approximately a 10m run and an allowance for fittings does show that 15mm would be too small and the velocity of water would be too great. So yes 22mm should supply the required flow rate to both, within the correct velocity to prevent noisy pipes.

(On an unvented in a average domestic property I would have gone 22mm to tee for kitchen then 15mm to both as a rule of thumb- but its nice to do these things properly occassionally)

Finally- its 12m for 22mm was what bs6700 used to state, which was why I raised the issue of sizing in the first place.

Knickers now untangled and am eating a small portion of humble pie

 

[Morris40]

Thats quite alright rojaca, I'm glad your knickers are now untangled, I know from past experience you don't sleep well with tangled knickers.

 

[rojaca]

that was tangled knackers

 

[Morris40]

maybe maybe not