Microbore tails to radiators

[sufferinghaggis]

I have a 5 bed, 3 bath Bovis built house 23 years old, we have lived here since new. The central heating system has been poor from Day 1 almost - it has a Potterton Netaheat Electronic 16/22 boiler which has run like clockwork with virtually no repairs needed over the entire time we have lived here. There are 19 radiators (some quite big ones) on the system. The heating is better upstairs than downstairs. The pump is Grundfos 16-50 130. Hot water has always been excellent - virtually impossible to run out. We have an auto bleed valve at the highest point in the system.

However, the radiators have always been, mostly, lukewarm and had required the system flushing at least every 2 years in order to keep them even at this level. (Very hard water area). About 5 years ago our plumber installed a pressure vessel and got rid of the previous gravity tank and this seems to have removed the need for flushing but the rads are still very poor in terms of heat output. There is no air in the system and I check the pressure regularly - the system has corrosion inhibitor in it but no magnatec device (one plumber suggested this may help but it has not been installed).

The upstairs radiator valves have to be virtually closed to get any heat at all in the downstairs rads and I have to be very careful to balance the smaller rads down to almost nothing in order to get any heat from the big ones.

I have had countless plumbers/heating engineers to look at it over the years - they all scratch their heads and offer the usual advice - new pump, power flushing, check the system balance, diverter valves, progressive rad bleeding, etc. etc. Nobody has been able to make any significant improvements or offer any revelations. Why I accepted the system in the first place when we bought the house from Bovis is beyond me, but it's a well insulated property and we have a mild climate down south so ... we put an extra jumper on when it gets cold.

Having now started to update and modify bathrooms and kitchen (floors up etc.) I have discovered that the majority of the system is plumbed in 15mm and the there are just 'tails' of 8mm microbore feeding the actual radiators. These tails vary in length from a few feet to several metres depending on where the rads are located. It appears to be a traditional layout of pipes apart from the microbore tails. I think this is a fairly rubbish way of plumbing the house but I would welcome anyone's comments.

I have, recently, replaced the microbore tails to 2 of the bathroom rads with 15mm (joining on to the existing 15mm incoming and outgoing pipework) and wonder upon wonder - we have 'proper' heat in these rads now !!

So ... is this a fluke ? or can I assume that I would be better to replace all of the 8mm with 15mm - it means all of the ceilings out of the ground floor as all the pipework is in the ceiling void (we have solid floors downstairs) but it might be worth it as we are thinking of selling the house and the poor heating is going to be noticed - or at least have to be identfied to a potential buyer.

I can do the pipework plumbing myself and it would be plastic for the runs across the ceiling void and copper down the walls - but I want to be sure that it is worthwhile before ripping the ceilings out. My present plumber (who has also failed to improve the heating) huffed and puffed and said it 'might be a good idea' when I phoned him. He told me that the microbore should come from a 'manifold' and then the pipes should all be of an equal length to all the radiators (clearly, in my house, this is not the case).

I would really like some clear advice. Sorry about the length of this post but I think you need to know as much as possible. Thanks everyone.

 

[kirkgas]

there is no doubt that 15mm copper is better than 8mm, although there are many systerms fitted 15yars or so ago with 8mm which work perfectly well, but are probably in flats with short runs from the main 22mm ring, we used to fit them all the time and it is best to fit the manifold centrally, but as you say yours may not be done this way, if the boiler works then changing the pipework will work, it is really your decision whether the work involved will be worth the end result. sorry didnt read your full post too carefully but have you had someone who knows what they asre doing to try to balance the system properly before going to this extent, perhaps the sludge etc is at such a level that renewal is your only option

 

[namsag]

What you tend to find in these circumstances ie straight from new.
Is as they have put the pipes in the have got sh~te into the pipes ,wood etc and it is stuck in a tee restricting flow or you do occasiuonally get a tee that has not got a positive stop in it and the pipe has gone in too far and has partially blocked the flow. and no amount of balancing etc will fix it.

16 rads,,,,,, 8 up 8 down , how many pipe drops are there ?? just one or several if just one this should be in 22mm

 

[sufferinghaggis]

Thanks Kirkgas,

I have had many people look at it over the years, without success, in fairness I think everyone thought it was a 'proper' microbore installation from a manifold but this appears to be not the case. Its a hybrid !

I think the basic design is flawed - the house is about 20m wide by 8m deep and the boiler is at one end of it and the pump/hot water tank at the other. I think the 8mm tails must be furred up or sludged - and the installation (with just the last few metres in 8mm both in and out of the radiators) cannot be ideal - anything that restricts the flow (and 15mm down to 8mm is a m ajor reduction) cannot be good news. The open tank installation which was in place for 15 years cannot have helped either.

I will wait and see what anyone else has to say but I have been reading other posts for the last couple of hours and I am getting the general opinion that, unless a microbore system has been well installed in the first place, it's probably going to give blockage problems or will be very prone to imbalance.

The only real solution seems to be to plumb the pipework to the rads in 15mm and then see what effect this has ... expensive, messy and time consuming but probably the only way forward.

Thanks.

 

[sufferinghaggis]

Thanks Namsag,

There are 15mm that come from and return to two long runs of 22mm in the ceiling void (presumably to and from the boiler ?) and this 15mm then goes to somewhere just above each radiator downstairs - the 15mm then is reduced to the 8mm microbore that goes down the walls to the downstairs radiators. In some cases there are several feet of microbore going across the ceiling (where 15mm plumbing would have been difficult) as well as the drops. Each ground floor radiator has its own drops down from the ceiling (the microbore pipes are behind the plasterboard dry lining). It's basically the same for the upstairs radiators and it appears to be from the same 22mm pipework. I have only seen some of the pipework where I have had to take floors up and one ceiling that had to come out as a result of a leak, so there are some sections of pipework I have not seen yet - so who knows what I will find !

I watched the house being built (thrown up !) in 1986 at the height of the property boom and was not immensely impressed with the site plumbers even then (messy, untidy joints, muck everywhere - I even caught them ignoring a completely folded microbore pipe - they were going to leave it until I pointed it out !) - but I knew nothing about microbore .... I wish I had been more aware then and taken more notice of what was happening.

Thanks again.

 

[kirkgas]

at the risk of everyone giving me pelters another option would be to connect onto existing 15mm pipe using 10mm (as you said some routes were difficult) but sometimes it was not too difficult they were just too lazy to do it right.
depends on what access you need or can get to fit the 10mm might not be any more than required for the 15mm, although you can feed the 10mm through, kind of depends on the long term plan for decorating, or staying in the house, your call really.

 

[Agile]

If you analyse which radiators are a problem you may well find that its only those with a long 8 mm feed.

You might well be able to just repipe those problem ones ideally with 15 mm but even 10 mm would be an advantage.

I went to a house on three floors where the downstairs had never worked in spite of about four visits. I found that all that was needed was the balance properly and particularly to balance the hot water cylinder coil.

Tony

 

[Razor900]

particularly to balance the hot water cylinder coil.

Tony

Totally agree, is there a balancing valve on the cylinder return?

Is there a bypass fitted to the heating system? If so what does it make a difference when it's closed?

What happens if you turn half the radiators off, do the others get hot?

Do your neighbours have the same system and do theirs work?

I'm assuming you have valves at both ends of the radiators and not double pipe entry at one end?

 

[Nige F]

15mm and the there are just 'tails' of 8mm microbore feeding the actual radiators. These tails vary in length from a few feet to several metres depending on where the rads are located. It appears to be a traditional layout of pipes apart from the microbore tails. I think this is a fairly rubbish way of plumbing the house but I would welcome anyone's comments.

I have, recently, replaced the microbore tails to 2 of the bathroom rads with 15mm (joining on to the existing 15mm incoming and outgoing pipework) and wonder upon wonder - we have 'proper' heat in these rads now !!


I
. Thanks everyone.

... You are polite calling that layout rubbish I`ve been there and done it , when working sub contract for BG .Mid 70`s Didn`t ask why they wanted us to do it like that, and you got the materials delivered to the house. Probably another cheapskate idea

 

[sufferinghaggis]

Wow guys,

Thanks for all of this - there are a few things here which I had not tried or considered so here's a few more bits of information:

1. If I switch off all the first floor rads the ground floor floor rads get marginally warmer - but I mean - the difference between lukewarm and warmish ! If I switch off the ground floor rads then the first floor ones get quite warm - a couple of them even get hand hot ! Don't get excited - its the two nearest the diverter valve in the airing cupboard and they are small ones ...

2. There does not appear to be any reducing valve on the return to the boiler so I can't see any way of balancing the hot water cylinder coil but this is an interesting idea as it stands to reason that water will take the easiest route ... if the microbore is clogged or even restricting flow then this could have an effect on the rads heating up as the water will, obviously, head off in the easiest route (28mm return pipe). The return pipe is accessible in the airing cupboard so it should not be too difficult to put a valve in there and try this - should I just use a standard gate valve ? There does not appear to be a bypass anywhere in the system that I can see that can be closed. Could I take the hot water out of the system by manually closing the diverter valve if I take the motor off the top ? I could then see what happens when the hot water is not in the loop ?

3. They are conventional radiators with valves at either end - they all have normal valves not TRV's - not a lot of point in TRV's is there !

4. At present I have only been able to get at the rad pipework in 2 bathrooms (under the floor) and some in the lounge (above the ceiling) - oh and a bit under one bedroom and the landing floor so it's a bit difficult to say which of the 19 rads have longer runs of 8mm - there is certainly some inconsistency across the pipework I have exposed so far but I suspect that the rads performing worst are those with long 8mm tails (guessing from their locations) - you are probably spot on with that Tony (Agile) and Razor900.

5. The 15 or so houses that were built in the first phase all have similar problems - rads that don't work, rads that are lukewarm etc. One of my neighbours had the whole lot ripped out and replaced but he was completely remodelling the first floor so he just went right back to the bare joists and started again !The later phases of the estate (although the same style houses) had different plumbers doing the installation and different boilers - their problems have been mainly with the boilers packing up not the radiators.

6. The rads with long tails that i have found are those where the pipes have to go at right angles to the joists so they have just banged a 10mm hoie in each joist and threaded the 8mm through like electrical cable - there are dips and bends all over the place as well - not even straight ! Hence - yeah - they took the easiest route possible and I am sure that it was Bovis building down to a price that instigated this poorly thought out arrangement. The house cost £265,000 in 1986 which was about the most expensive estate house in the town ! (I was rich in those days !!) Perhaps my comments about the quality of the design and installation have been tempered by years of living with it ! I am not a plumber - but I have to say my end feed joints are kings compared to what the cowboys who did the original job left behind !

7. In terms of fixing the problem I think that I can get to the pipeqork for about half the radiators by taking down the lounge, dining room, garage and hall ceilings - it's a pain but it's not the end of the world. I will use 15mm plastic for the runs across the line of joists which will make it easier and use copper wherever I can (I am not a fan of plastic). The house has artex ceilings and needs decorating so it's a good time to do it if I have to. The floors upstairs are 22mm (no its not 18mm - I've made that mistake) chipboard and they are beggars to get up. Some of the pipework is so close to the underside of the floor it's dead easy to nick it or bend it when you try and get the boards up (They come up in sawdust anyway !).

8. I may get someone to have another go at balancing the system and include the hot water cylinder return and see what that does but I guess if no significant improvement then it's probably best to do the work before we get to winter - cold showers will be OK now but not a lot of fun in November.

Thanks for all your comments guys - very much appreciated. Great forum ...