10mm copper microbore, to replace or leave

[cascas]

In the process of renovating a house, so floorboards up etc.

currently, 22 to manifold in landing, 10mm micro to Bedroom 1 & 2 and hall (6-7 metres each from manifold, 15mm running from just before the upstairs manifold downstairs (3-4metres), and again in microbore (3m to dining room, 3m to kitchen, and 4-5 metres to lounge).

Initial feeling was to pull all the microbore up, and replace with plastic. But now undecided if to use plastic, copper, 10mm plastic (no better off than the copper micro), or just leave it as it is, and just change the radiator tails to 15mm copper

I have used plastic extensively previously, but prefer to use with brass compressions, never really used many speedfit connectors.

After looking at it more, I am tempted to reduce to amount of microbore, ie change all upstairs to 15mm hep2o, if not remove all of it.

What would others do in this situation.

 

[PowerFlushAssoc]

Try NOT to have micro bore in your system, they tend to block up and they are really hard to unblock.

 

[PlumbBobBob]

only if you don't keep the system dosed with inhibitor and change the water every so often

 

[tamz]

Try NOT to have micro bore in your system, they tend to block up and they are really hard to unblock.

They may be hard to unblock but on a correctly piped system they will not block in the first place. So much for the secrets of powerflushing microbore :wink:

Personally i would suck it and see. How are the rads performing atm?
The biggest fault with microbore is excessively long runs and oversized (for the available supply) rads.
10mm plastic is approx the same as 8mm copper so will be worse off.
Decide for yourself based on how the system functions and change it if you see fit.

 

[cascas]

Not sure to be honest, there was an ideal boiler, that will be replaced with a combi. old boiler was fitted a couple of years ago by British Gas, but not sure if pipework predates the BG install.

 

[tamz]

Nearly all 8mm will be 70's early 80's. !0 mm will be 80's 90's. Some 10mm systems are still fitted but few and far between unless plastic and 8mm even rarer.
Big gas brainwashed the populous into 15mm but they were the ones pioneering 8mm at the time.

 

[Best]

If it was my own house & money not too tight, then I would rip it all out & use copper pipe - but no microbore. Some of the runs are not very long, but that is on both pipes, so it's double the length. 15 mm pipes to supply downstairs is not what I would want. As Tamz said, 10mm plastic has smaller bore. If it is half decent system & clean, you could just improve any bits you can, new rad valves, ( with 15mm to 10 reducers if u wanted) as it could do for years.

 

[cascas]

What is the maximum KW that can be put on 15mm flow/return. I seem to remember that it was about 4kw - but has this changed for condensing boilers?

 

[tamz]

Approx 6kw recommended but in reality a good bit more on a sealed system.

 

[Best]

My max on 15mm if you really had to would be nearer 6 kw & perhaps more on sealed systems. So your " 4 kw" is a safe good max to not exceed. I tend to only do one large rad max, from 15mm or 2 or 3 smallish rads from 15mm if possible. Only issue with condensing boilers, is if they are run at low temp to keep in max condensing mode, then heating the rads will be worse if pipes too small bore/ long runs to start with.

 

[cascas]

Looking to replace the existing 15mm feed hat supplies kitchen / dining / lounge in micro, with 22mm, and then run 15mm to kitchen, dining, lounge & also add in hall to save another pipedrop.

 

[tamz]

Nothing wrong with that.

 

[jncalderc]

Personally I think if your system is going to sludge it will regardless of pipe, Our house which is a 5 bed and 3 bathroom runs more than adequately with 8mm microbore from a combi without any problem at all and the house is 18years old. I find the biggest pain with 8 and 10mm is that the compression fittings only need a little knock to come slack and leak, best to use hawk white on them. Ptfe is a pain

 

[Best]

I find the biggest pain with 8 and 10mm is that the compression fittings only need a little knock to come slack and leak, best to use hawk white on them. Ptfe is a pain

Microbore to rad valves tend to leak easily, so I would prefer using 15mm rad valves & soldering 10mm x 15mm reducers ( 15 mm male type) on to end of pipes. This means it is hard copper you are compressing olive on to, so won't leak. I always use paste still.

 

[stevetheplumber]

Nearly all 8mm will be 70's early 80's. !0 mm will be 80's 90's. Some 10mm systems are still fitted but few and far between unless plastic and 8mm even rarer.
Big gas brainwashed the populous into 15mm but they were the ones pioneering 8mm at the time.

most new builds in the south are 10mm plastic tamz major advantage is it can be cabled in from below so floors can be laid earlier ground floor rads are run down from above behind dry lining

 

[tamz]

Same up here Steve. Dropped to behind rad. It is actually a good way of doing it imo