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Discuss Power flushing blocked microbore in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

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3
I am a homeowner after some advice about power flushing a central heating system with microbore pipes that seem to be blocked.

When I switched the boiler on in October, 3 of 12 radiators never warmed up and 2 other radiators became only lukewarm. My plumber concluded the pump in the 11-years old Vaillant combi boiler was gone and he recommended installing a new boiler, rather than repairing the old one, as it was past its shelf life.

He installed a new Vaillant boiler (with magnetic cleaner) but nothing's changed. He used the boiler and the vac to flush/clean the system and specifically one of the offending radiators, also reversed the flow in the system, but nothing helped. He disconnected one of the cold radiators, cut a pipe about 5m away and closed off other radiators in the loop, then used the vac but the air wouldn't get through. It seems the section of the piping is totally blocked. There is probably another section on the other loop equally blocked.

All the pipes are under the chipboards and behind plasterboard. We cut an opening to the chipboard and saw that there is a mixture of plastic and copper pipes - some 22mm, some 15mm, but the last bits going to the rads are 10mm microbore pipes.

The plumber recommended either replacing the pipes, or power flushing the system. Repiping the house would be a lot of mess and hustle, so I opted for power flush, fully knowing that it may not work.

I put Sentinel X400 to the system 2 days ago. I haven't drained the system yet to see if there is any sludge there, but so far the only improvement is one of the newer radiators heats up better than before. On the downside, the 2 radiators that used to be lukewarm are now totally cold. 😒

My plumber doesn't do power flushing so I found a different plumber who is coming to do it in 3 days. However, after reading about power flushing a bit, I am now not sure whether it is worth doing it at all.

Can you clean blocked microbore pipes by power flushing the system?

Is it a waste of time and money? Should I just go for repiping the house, or is there a different option there?

I realised the plumber should have cleaned the system before he installed the boiler. I am not sure what exactly he did, maybe he chemically flushed it, I don't know. I am also a bit upset because we probably threw away a perfectly fine boiler, maybe we didn't really need the new boiler after all. Well, there's no going back.

Please advise. Thank you.
 
A

Aquarius

No amount of chemicals or flushing will clear a solid blockage. Has anyone tried to balance the system? Do you have confirmation that it’s blocked? If so, how? Anyone tried disconnecting the flow/return pipes for checking flow of water? When you say used a vac, do you mean a wet vacuum cleaner?
 
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Messages
3
No amount of chemicals or flushing will clear a solid blockage. Has anyone tried to balance the system? Do you have confirmation that it’s blocked? If so, how? Anyone tried disconnecting the flow/return pipes for checking flow of water? When you say used a vac, do you mean a we try vacuum cleaner?
Yes, the plumber tried to balance the system. Even with all rads closed and just one open, those that usually never get warm do not heat up.

I don't have a confirmation that it is blocked as such. The plumber disconnected the radiator. He closed off other radiators in the loop. He then cut the plastic pipe that feeds that radiator about 5m away from the radiator. He used the vacuum cleaner to suck the air from the pipes but doing it one way (sucking by the radiator) did nothing. When he connected the vac to the other end of the pipes (where he cut it), there was a very slight suction in the pipe by the radiator.

The radiator was completely removed and the flow/return pipes were connected by a hose but there was no flow through it.
 
A

Aquarius

Can they still get kinked somehow?
It depends on how loose they are, they could droop and kink if not clipped properly. Other than that, not normally. Could be a blockage I suppose, but probably cheaper to re-pipe, as if they’re that blocked, then powerflush doesn’t generally clear blockages.
 
Messages
851
A couple of points.

As you have probably worked out your installer was just guessing. It is not difficult to determine if a pump is weak, if there is no or reduced flow in a system and indeed where a pipe is blocked with magnetite (use a magnet on the pipe).

For power flushing or chemical cleaning to work on any hydraulic system you must have at least some minimal flow. If you have no flow ie a total blockage you then look at hydrodrilling - but you would not go to that solution for a domestic heating system. Full or sectional replacement is the only realistic option.



You appear to have had a new boiler installed into a very dirty system - whilst you have a magnetic filter on the return it does not catch everything. If you have reversed the flow with the new boiler connected it offers no protection at all. You are at a very real risk of (or have) introducing sludge / magnetite into the new heat exchanger as and when debris becomes loose in the system.

From what you describe, a repipe is probably your only option - but I would also have the new boiler properly cleaned too.

if you want to delve further look at or near the manifolds - sludge starts to build up at points where the flow velocity changes
 
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Ruth Donna

I have a blocked return pipe from the hall radiator currently. I tried connecting a hosepipe with mains water pressure to it, which didn't work - neither did connecting a foot pump and pushing 5 or 6 bar of air pressure up it either (all that did was blow air into the kitchen radiator but not clear the blockage). So my next tactic is to shove a 10-metre length of net curtain wire up it when it arrives from Amazon later today - which will hopefully physically clear the blockage. If that doesn't work, I'm going to have to cut into the ceiling below the airing cupboard to try and access the manifold (which I think will most likely be there) and try re-piping - which I really want to avoid if at all possible!
 
A

Aquarius

So my next tactic is to shove a 10-metre length of net curtain wire up it when it arrives from Amazon later today - which will hopefully physically clear the blockage. If that doesn't work, I'm going to have to cut into the ceiling below the airing cupboard to try and access the manifold (which I think will most likely be there) and try re-piping - which I really want to avoid if at all possible!

Good luck, I can probably safely say,you’ll be be re-piping it.
 
Messages
851
Blockages generally occur when pipe diameters change along with flow velocities, so debris drops out of the pipe flow and starts to build up.

In short the blockage is likely to be at the manifold or a valve, not in a straight length of pipe unless it has been deformed.

Be careful trying to remove a blockage by pressurising with air - if the pipe or a joint fails it will explode as the air instantly expands to atmospheric - if you pressurise with water, if the pipe or a joint fails you just get wet (water under pressure is not compressed, air is)
 
D

David Caisley

I had the very same problem with my system in as much as all the pipe work is 10mm copper which became eventually blocked over time. On the recommendation of a friend who searched the internet and found the answer to the problem, if you go onto YouTube and search for ”GALLO GUN” you will see how it works, it is very simple and should cost no more than £60 plus cartridges, basically it fires a small compressed air charge of 800psi clean air through the pipe and shifts whatever blockage there is, it is made for refrigeration engineers who often have to clean out small pipes on the fridges. I had to go up into my loft and cut every pipe either side of the ancient manifold and inserted into every pipe a piece of tissue to block off the end of the pipe and the got my son to go to each rad in turn and remove the copper pipe from the valve, and then fire the gun into the pipe, this would then show me which pipe to which rad. we were working on as the tissue would fire out into the loft thereby letting me label each pipe flow or return, beware when the magnetite explodes from the pipe you can get covered in muck as my rafters show. Good luck and I am sure this will be the simplest, cheapest and cleanest solution to your problem, no ripping out flooring or walls etc. All you plumbers out there should look at the Gallo Gun because it will get you out of lots of problems.
 

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