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42 year old open vented system on microbore

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Discuss 42 year old open vented system on microbore in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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R

rick

Hi everyone,

I'm a new member and not a plumber or central heating engineer.

Mum and me live in a 1970 house she's had from new and the installed central heating is very primitive (no thermostats except the one close to the Concorde boiler, no zonal valves). As far as I know, it's never been cleaned. On the Concorde, the electronic ignition gave up long ago, but apart from that everything works fine. All radiators are hot, there's no leaks and none ever need to be vented. It's even got some ground floor underheating due to the presence of the microbore pipe runs! Maybe it's living on borrowed time? (there is a fair bit of kettling!)

Either way, looking to have a groundfloor extension made, so that Mum can live downstairs. Extra rooms needed for bedroom, downstairs bathroom etc. Therefore, will need to add extra heating and will look at the very least to change the boiler to go along with the extra piping and radiators. How further does everyone thing I should go? As it's microbore, should the whole system be replaced? Or, should the system be cleaned and flushed, radiator by radiator; then pressure clean the system as a whole; then change the boiler; then add the new piping and upgrade with thermostats? I've had a few opinions from both builders and plumbers. One suggested keeping the piping and changing the rest, the others to change the whole system. A major disruption to change the piping:- either buried in the solid ground floor or twisting everywhere under the upstairs floorboards. Your opinions all gratefully accepted!

RicK
 
I would of said spend the bit extra money and re-pipe the whole lot, with zones etc. What you spend out now you should save in gas later on if your planning on staying in the house for a while.
You will be cursing yourself if after all the work it develops a leak in the screed or other problems occur.
Thats my opinion other people may disagree.
 
hi rick unfortunately microbore is difficult to flush properly and for the heating you would need to see the condition of the matrix really. if the system has been down that long, never cleaned i would say that you may be living on borrowed time and when/if you do get issues in the future it will equal unexpected disruption and expense. IMHO i would upgrade all pipe work as that will allow you to factor everything in and get exactly what you want in your syrtem. Really it comes down to do you believe in preventative maintenance or the if its not broke dont fix it rule.

good luck
 
Thanks. It's just that I'm keen to attempt to keep as much of it that's sound as possible:- especially as far as having to lift all the upstairs floorboards. Also, are new radiators as tough as the old ones? Or do you change as a matter of course? As it's microbore, is it likely to fur-up/leak then? I was looking to have the system all cleaned/inspected before the work proper started, to have some confidence in the piping as it is now.
 
Also same as others maybe worth a going over from scratch if microbore buried in concrete, definitely wouldn't recommend pressurizing it asking for trouble, and only listen to the advice of plumbers builders like to think they know and can do more than they can imho
 
Thanks for all these fast responses! We never work this fast in Aerospace!
 
Re-pipe / zone as others have suggested. With the building work you are going to have a lot of disruption so you may as well get it over in one shot.
 
i also agree, i employ a few rolls royce workers to maintain my 4 jets :smartass2:
well, it costs nothing to dream,

i've got 4 jets though, i took them out an old gas cooker :biggrin:
 
Wish I hadn't mentioned the aerospace bit! Since then no one's said anything about the heating system! So, do all the radiators go and replace them with new ones? They have twin valves in. I assume a combi boiler? The house has currently four upstairs bedrooms & one bathroom. Planned a new Mira thermostatic mixer shower downstairs. No plans for an en-suite upstairs. The current upstairs shower I assume should work better. It doesn't need to be changed to a thermostatic mixer due to safety regs. does it? (I'm sure it would if Aerospace engineers were involved in the safety aspects!)
 
rick said:
Wish I hadn't mentioned the aerospace bit! Since then no one's said anything about the heating system! So, do all the radiators go and replace them with new ones? They have twin valves in. I assume a combi boiler? The house has currently four upstairs bedrooms & one bathroom. Planned a new Mira thermostatic mixer shower downstairs. No plans for an en-suite upstairs. The current upstairs shower I assume should work better. It doesn't need to be changed to a thermostatic mixer due to safety regs. does it? (I'm sure it would if Aerospace engineers were involved in the safety aspects!)
Click to expand...

You did bring it on yourself :smilewinkgrin: Never assume a combi.......rads will be past their best and unlikely to be convectors and if dual entry a pain. You could always add a pump for the shower although most gravity ones will work well if you do the combi thing.
 
Do you mean twin entry valves? (both pipes go into a single valve at one end of the rad.) If so, get them changed at the very least. I wouldn't advise fitting a combi to a system with pipework buried in the screed. Combis have pressurised heating circuits, combine this with pipework buried in a corrosive substance, you can guess the outcome.

If you have a mixer shower with hot and cold feeds, you should get much better flow from it using a combi.
 
Both of the plumbers suggested combi! My past experiences are not good due to long pipe runs to both kitchen sink and shower. Also, Mum still likes an 'airing cupboard'!
 
Yes, sorry, I meant twin entry valves. I'm fairly acceptive that I'm changing boiler, all radiators and all pipes!
 
its upto you what system you want mate just if only you and mum then a combi will be cheapest to run. If there were more people and an ensuite i would be looking at new unvented but the cost is a lot higher for this type of system
 
if you like the airing cupboard and the runs for hot water are long you can fit a open vented boiler with either a conventional cylinder use a mains fed one although its on borrowed time you could reuse the heating circuits and rads as they are but it would be a gamble spend now or spend later its a financial decision rather than a plumbing one
 
Yes, thanks, I thought it might be that trade-off. Chicken and egg really. One bedroom would nicely have an en-suite if the hot water tank wasn't there! Perhaps get the hot water tank and boiler both down stairs if a new unvented??? Not massively worried about the running costs - having had a 55% efficient boiler for 42 years, still a big improvement!
 
I assume if needing to move the hot water tank, go for a new one and switch to unvented? It's that or go for the cheaper to install combi, cheaper to run, but no room for further expansion. I'm asking all this on the forum in case the engineers I've had are pro-combi!
 
Hi again all.

So I've decided best to go for a full new system.

I'm not a combi fan, but I like the sound of the Valliant 937 with 7 years warrantry. That would allow the removal of the upstairs cylinder and this would then give the space for an en-suite in the future. Is the 937 the best of both worlds then? Will it handle 12 radiators, two showers both on at the same time?

If it was sited where the current boiler lives that would be fine, then pipe runs not too long. However, the plumber said the flue/vent needs to be 600mm away from the adjacent, protruding outside extension wall. Seems a bit excessive to me? Is that correct?
 
Shame, micro bores are the most efficient system as the water content is very low they've had micro bore on the continent forever. Unfortunately the British system of open systems does not lend itself to this type of system because the continual venting (open Tanks) mean that the water is continually changing and causing oxidization and eventual sludging, a well designed micro bore pressurized system is the bees knees.

The only reason for 15mm pipes is because they don't block as easily, and you wont get sludge in a pressurized micro bore, unless something is wrong, Ive installed a lot of microbores using the radial system i.e. manifold in the middle of the house and 10mm plastic leads to the rads heats up in a matter of minutes if not seconds.
 
Thanks. Yes , it all works fine now, but foolish to risk it really. Not been cleaned for decades now. I thought about going for a clean before changing the boiler, but I'd always worry about the buried microbore. I did get a quote to clean each radiator in turn rather than pressurise the old piping and then go for a new open vented boiler.
 
chances are if the pipework in a 42 year old system has not leaked so far then it wont, copper was of a much better quality and a lot thicker then not to mention better tradesmen (tongue in cheek) who knew how to lag pipes.
 
I've had a plumber round about doing the whole system. The cost isn't the issue, but full new piping involves having to drop two 15mm pipes down to each ground floor radiator in conduit( solid walls & downstairs is solid floor). All the cornicing etc. will be messed up! I can't think it will look well.

Another plumber suggested keeping the microbore and going for a combi. Cut the microbore close to the rads and replace the twin-entry valves with single entry at either end. Ie. convert from microbore to 15mm locally around each radiator.

Opinions, please?!
 
Will the existing manifold arrangement (whatever it is) and microbore work with combi/unvented/system alike?

Should I first get it all cleaned and flushed as the system stands with the old cast iron boiler that can handle dirty water Ok? Or can the microbore be cleaned separately after the radiators come off for valve changing?
 
Thanks, is that to check if the existing microbore could still be used? Is it somehow done on each pipe stretch, from manifold outlet to manifold inlet somehow?
 
Disconnect boiler, cap open vent and cold feed and test whole system. Sealed system prv will blow off at 3 bar, based on safe leeway I'd go to 4.5 bar and see if you get any drop.
 
Thanks, a bit over my head, but will relay that to the plumber. I assume if the system handles the pressure it is Ok to go for a pressured new system with the old pipework?. If there's problems I suppose I'll have to get a complete new system.

If the old system does handle the pressure then I was thinking to go for a veissmann 222 / vailliant 937; getting rid of the cylinder and old radiators but keeping the microbore and pipework largely as it stands. Will there be any old sludge in the pipes to get rid of? Would the new system somehow flushed to get rid of sludge prior to the boiler being started?
 
yes there will be plenty of crud laying in the pipe work so a power flush before the new boiler gets installed is a must and i would all so fit a tf1 filter on the system hope this helps
 
Cheers Phil. I think it's all getting alot clearer now!

I'll look to get old system pressure tested at simonG suggested. If all OK then get rid of old boiler, cylinder and rads. Then new rads and TRVs fitted onto the old microbore. Then as you suggest, power flush and have new filters put on. Then have installed new combi boiler with it's own local hot water reservoir for fast hot water response....

Does that all sound something like how to have it done???....

If the microbore goes kaput, then or in the future, I suppose the floor boards go up and the pipe drops have to go in!
 
You could always look at fitting an intergas. These can be used as open vent combis.
 
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