Hello and help with a microbore system!

[Jimboliana]

Hello everyone,

I have just moved into a 4 bed house which needs a bit of doing up, the heating/hot water is my main concern. The house was built in 1985 and has microbore for the central heating and some of the rads don't get hot. The boiler is an ideal HE24 fitted in 2007 which is in the garage (attached to the house) which feeds the old hot water tank in the airing cupboard. Two tanks in the loft. Three way valve in the airing cupboard for the heating/hot water I assume?
The two rads in the bathrooms (main and en-suite) only come on with the hot water so I assume they are on a different circuit to the main heating?
All the rads in the house apart from one (in 2006 there was a small extension on the back of the kitchen and an extra rad fitted) are fed with 8mm microbore where the pipe goes into the wall (dot and dab I think)
No TRV's on any of the rads in the house
There are two rads in the kitchen, the original on 8mm microbore and a larger twin that is fed with 15mm copper which does not seem to get hot at all (lukewarm on one side if i'm lucky)
I don't know where the mainifold is for the microbore yet
I also only have a 15mm cold water mains feed coming into the house!
I can't change the microbore so the plan is the following and this is where I need opinions

• Pipe the 15mm into the garage and through a water softener with a bypass (very hard water in Essex and leaving the mains to feed kitchen tap and outside tap)
• This is to fill a 180ltr tank (Grundfos slave home booster tank) it was free and new and left over from a job
• Through a new free Grundfos Scala2 pump to feed a 250ltr - 300ltr OSO unvented twincoil (might add panels later) cylinder for my hot water - located in the garage as well - four of us in the house - 2 adults, 2 kids
• Change the boiler for a heat only and pressurise - add a Magnaclean or such like
• Fit a Grundfos Alpha3 CHP to help balance the system
• Rip out the old rads and powerflush the microbore
• Fit new rads everywhere
• Fit the Honeywell Evohome on the rads and for the hot water

Now please tell me what potential issues I could have and any advice is welcome

Thanks for looking
Jim

 

[oz-plumber]

Just to begin: .....
......34 year old microbore piping and probably 34 year old panels and valves.
The pipework is probably past its use by date. I read somewhere that the piping used back then had a 30 year life cycle.
You may end up with a lot of problems in the near future.

I would begin with replacing the whole system.

 

[ballvalve]

Rip it all out and start again.If you are having a new boiler and unvented cylinder do the job right.

 

[Stigster]

Ripping out the microbore is the last thing OP wants to hear I'm sure but seriously, with all that thought and all the expense that they are going to I can't say with good conscience it would be a good idea to keep the old microbore. 8mm just makes it even worse and less worth keeping.

If I were in a position to take on that install I don't think I could do it with the old microbore system in there. I just wouldn't want to. Sorry Jimboliana.

 

[king of pipes]

I have to agree I am afraid if you are going to the expense of a system upgrade it is false economy to use the old microbore replace it you won't regret it . Kop

 

[Jimboliana]

Stigster you are correct! The problem with ripping it out is that it is in the walls. The pic is from the lounge under a window on an outside wall though the internal walls are dot and dab I think. I would have to rip half the walls apart to trace it though I would be 99.9% right that it all went up to under the ceiling as the floors are concrete.
I was going to change all the valves/lock shields on the rads as well.
What I don’t understand is some people think microbore is fine as long as you look after it and after a power flush it should be like new?
(I might be trying to convince myself!)

 

[ballvalve]

Take out what you can see,fit new rads new pipework smallbore.Old pipework stops in the walls.

 

[Jimboliana]

Ballvalve, I think that is a good idea, if we can find the manifolds I will see what condition they are in and change them as well if they are bad.
The plan would be to run the system over the winter to see how it performs and before we do any redecoration anywhere.
If it is no good then I will investigate further and rip it out the walls if I have to.
I am hoping the Alpha3 will help with the balancing of the system. I think its just an inverter driven pump, ramps up and down as and when rad valves open?

 

[Stigster]

Stigster you are correct! The problem with ripping it out is that it is in the walls.

I fully understand your dilemma. If you are left with no real choice but to reuse the microbore system, as it is several decades old at this point I would at the very least want the hidden pipework properly flushed and then pressure tested. It would be wise do a chemical clean to loosen up any hard deposits in the week or so leading up to the flush.

After the flush please do get it pressure tested as you are planning to convert to a sealed system. If the hidden pipework is clear, clean and tested then you can go ahead and use it. It's not ideal but I understand why you don't want to rip it out and we don't live in an ideal world so as long as you can be confident the pipework is sound, you can make it work. It's certainly not a job to just cross fingers and hope for the best!

 

[Jimboliana]

Stigster,
Spot on and good idea to pressure test it after. We have all the gear for pressure testing as well
One of the guys that will be doing it does work for me and is a qualified plumber so we are calculating the size of the rooms for the rads etc. and to size up the boiler. But it is always good to have other peoples opinions/views that may have had more experience with these things. He has a power flusher and as I say we were going to take the rads off and power-flush the pipework.
He doesn't seem to think I should need to add any chemical before the power flush as he has said the power flusher should strip it back to bare copper?

 

[Stigster]

I suggest the pre-treatment because you already appear to have some blockages going on and also that microbore is not the easiest thing to flush. Powerflushing works on high flow rates rather than high pressure so if the water cannot flow it cannot clean. A high throughput of water is already limited by the small 8mm tube (8mm is the external diametre so the bore diametre is even less). Putting a cleaner into the system for a few days will hopefully break down or loosen these blockages and allow the flush to do its job properly. All learned through personal experience after being told by several people "you can't powerflush microbore!"

It's not essential but it's an inexpensive and easy thing to do. It's what I would do in a system like that.