Max distance for 10mm tails off 22mm flow and return

[smallsteve]

I’m considering my options for moving (JG) pipework from an inaccessible place whilst the floor is up. One option might be to use 2 x JG 4-port manifolds, mounted in a much more convenient location. But, this would mean adding 2 - 3 metres to the 10mm tails (off flow and return) and i’m not sure whether that is a good idea?
Reason i ask is because i note that whoever installed the pipes originally, took the 22mm f&r as far as they could, even though it was not easy to do so. This makes me think that there was good reason for doing this and hence my reservation about changing it!
TIA

 

[Ben-gee]

Yes do it, it will be fine.

 

[smallsteve]

Yes do it, it will be fine.

Cheers Ben. Out of interest, when does length of the tail become an issue, accepting that shorter is better i.e. what length would be considered excessive? I’m curious as to why they went to so much trouble in getting the 22mm pipes extended, when it would have been considerably easier to drop 10mm pipes down the boxed-off area. TIA

 

[Stigster]

It's the heat output of the radiators that is the deciding factor on the pipe sizes, rather than distance, in a domestic situation at least. The original installer took 22mm as far as he could basically because it's the "proper" thing to do and he was probably a decent guy so put the effort in. A manifold is a good solution for you as well though, nothing wrong with doing that.

As Ben-gee says, you'll be OK with that relatively short run of 10mm unless the radiators are freaking massive.

 

[smallsteve]

It's the heat output of the radiators that is the deciding factor on the pipe sizes, rather than distance, in a domestic situation at least. The original installer took 22mm as far as he could basically because it's the "proper" thing to do and he was probably a decent guy so put the effort in. A manifold is a good solution for you as well though, nothing wrong with doing that.

As Ben-gee says, you'll be OK with that relatively short run of 10mm unless the radiators are freaking massive.

Cheers Stigster. Did wonder if it was something to do with potential blockages with these smaller-diameter pipes and hence, keeping lengths as short as possible. As mentioned, worst-case would only be an extra 3m and the radiators aren’t large. Just wanted to be sure before doing in haste and regretting at leisure! It will be buried under tiles at some point and so i won’t easilt get chance to correct my folly! :-/

 

[Stigster]

10mm pipe is more prone to blockages for obvious reasons (smaller bore of course) but the proper answer to that is to maintain a clean system. If the system starts out clean and you have the correct dose of corrosion inhibiter it'll be fine. 10mm becomes a problem in very poorly maintained systems, as you could imagine some are.

Your question was perfectly valid.

 

[smallsteve]

10mm pipe is more prone to blockages for obvious reasons (smaller bore of course) but the proper answer to that is to maintain a clean system. If the system starts out clean and you have the correct dose of corrosion inhibiter it'll be fine. 10mm becomes a problem in very poorly maintained systems, as you could imagine some are.

Your question was perfectly valid.

Thanks again and you’ve put my mind at rest!

 

[SJB060685]

You also have to consider the pressure drop of 10mm pipe. Large runs of 10mm will have considerable pressure drop, which can result in the pump head not being sufficient. This leads to larger pumps needed and increased running costs.

 

[smallsteve]

You also have to consider the pressure drop of 10mm pipe. Large runs of 10mm will have considerable pressure drop, which can result in the pump head not being sufficient. This leads to larger pumps needed and increased running costs.

Hmm OK, but what do you class as ‘large’? This is where my issue comes in, as it becomes subjective and i don’t know where the boundaries are!? Are you suggesting it may not be OK in my circumstance described above?

 

[Aquarius]

I seem to remember reading a maximum of a 5 metre run of 10mm on radiator circuits, not sure if that’s changed.

 

[SJB060685]

Hmm OK, but what do you class as ‘large’? This is where my issue comes in, as it becomes subjective and i don’t know where the boundaries are!? Are you suggesting it may not be OK in my circumstance described above?

Ok. This is an example from my design guide.
A 1 metre section of 10mm with a flow rate of 0.034 kg/s, or 0.034 litres/s has roughly 0.060 metres of head pressure loss per metre.
What you've mentioned above should be fine, I was merely pointing out the problems if the runs were excessively large.

 

[smallsteve]

Ok. This is an example from my design guide.
A 1 metre section of 10mm with a flow rate of 0.034 kg/s, or 0.034 litres/s has roughly 0.060 metres of head pressure loss per metre.
What you've mentioned above should be fine, I was merely pointing out the problems if the runs were excessively large.

OK, thanks for clarifying.

 

[Last Plumber]

It depends (as mentioned above) what the flow requirements of the emitter/emitters are in order to provide the performance needed. Other factors come into this too, such as what type of system, the length of run, pipe size, pump size etc. It isn't as straight forward as a rule of thumb method, although people do use them based on their own experience.

 

[Stigster]

I would not be worried about 3 metres of 10mm coming off the 22mm even if it was going up a floor but yes, with longer runs and going up in the building frictional losses can become a factor. With you only going 3 metres in any direction I would not expect any problems at all.

The lads are all correct of course and these things cause very real problems when things are marginal on the figures but you'll be right with what you are asking.

It's all useful and informative stuff that's for sure.

 

[smallsteve]

I would not be worried about 3 metres of 10mm coming off the 22mm even if it was going up a floor but yes, with longer runs and going up in the building frictional losses can become a factor. With you only going 3 metres in any direction I would not expect any problems at all.

The lads are all correct of course and these things cause very real problems when things are marginal on the figures but you'll be right with what you are asking.

It's all useful and informative stuff that's for sure.

Appreciate the update / further confirmation, along with everyone else’s input. As you say, it’s all food for thought. When i saw mention of 5m max, that would have been pushing it!

 

[Ben-gee]

Steve, the more you look the more different answers you will find.

Consider the source of the info you are looking at and why it has been put there.

If you find a consensus of opinion on this forum from the names you see time and again offering great advice- I would go with that info.

Some of the guys on here should be charging for their knowledge.

 

[smallsteve]

Steve, the more you look the more different answers you will find.

Consider the source of the info you are looking at and why it has been put there.

If you find a consensus of opinion on this forum from the names you see time and again offering great advice- I would go with that info.

Some of the guys on here should be charging for their knowledge.

Indeed and i fully understand that. Your original response was sufficient for me and i respect your opinion, as well as being grateful for the number of times you have answered my (endless) questions.
Always happy to engage with other opinions though, as it helps to learn more about the subject. I am an engineer myself and so interested in the technical reasons as to why someone may have a contra-opinion. That’s not to say that i have ignored previous advice, or not taken it on-board.
Thanks again.