how do you clear blocked underfloor heating pipes?

Question

I have a 1988 liquid (water) underfloor heating system heated from a conventional oil boiler. The main system was from a 6 branch manifold where each branch fed through a PARRALEL network of pipes under a certain house floor plan section. The manufacturer likened it to 'radiator' sections under the floor. I now see that this is totally crap as water (or most things) flows through point of least resistance and therefore, this allows sediment to build up in 'radiator' sections under the floor. Last time this happened when we changed from a Rayburn solid fuel boiler to the oil boiler, we managed to clear most (if not all) the sections by feeding the circuits with some sludge remover liquid over some weeks and then refilling with some preventative solution. That was around 6 years ago and it's been OK since then. This last work has been caried out by ' someone who knows everything' and now the stystem is blocked because he did not flush the system through and treat with preventative. ????

Yes, I have tried to disconnect each end of a branch pipe and individually let the water flow through with the 2 Bar pressure from the system. It trickles through so I guessed that the longer it could keep trickling, then the fernox that I had put in would eventually loosen the scale and it would dissolve into the liquid to be flushed out.
The danger though comes from when I tried to pressure wash through a larger 15mm flow and return pipe to an extension. The silt just backed up against a blockage and the pressure 'blew' the pvc pipe (fortunately) just where the pipe entered the concrete floor. I obviously do not want to run the risk of blowing any of the joints in the parallel system under my main floor and therefore am wondering if anyone knows how to create a vacuum on the other end of the pipe to draw the residue out. I imagine something with a drop cannister/box to drop sediment into and yet be able to top up the vacuum as the 2 bars pressure pushes from flow side. Anybody??

By the way, the plumber who has recently moved the boiler is blaming the stainless steel inserts in the platic pipes for creating the sediment and says that now they are not being used and plastic ones are being used instead.
My own research suggests that filth and residue arises from when any work is done on a system and needs flushing out with the cleanser solution (as was done in 2000 when my Rayburn was changed for an oil boiler). The system then was fitted with the protecting solution and all was fine.
How comes my local builders supply has just supplied me with two stainless steel inserts if my plumbers words are true?
I thought that corrosion from steel radiators, boiler parts and residue from plumbing connections created this silt.

He also infers that all these underfloor heating systems installed over the last 20 years will create the next 20 years work for plumbers to install conventional radiators systems again.
Thoughts???

Answer 1

You will need to have it power flushed to get the sediment into suspension and clear it completely, I assume that it's plastic pipework, contact Fernox for further advice.

http://www.fernox.com/index.php?cccpage=technical

Answer 2

The underfloor heating circuit should be pressurised when the concrete screed is poured and left pressurised until the concrete has cured. There are several different methods of laying UFH in concrete depending on the design of the system.The most common method from the ground up is concrete foundation,insulation resin board(Kingspan),membrane,heating circuit then screed.The screed will be on average around 4 inches thick. There should be a blending valve on the circuit to prevent the water temperature rising above 50c.

Answer 3

Hi I have a blocked underfloor heating circuits and about to power flush it myself a week Friday. How did you get on in the end? Did you have to resort to air compressors?

Best Ken

Answer 4

disconect the feed and the return side for that zone and try an air compressor with a regular air nozzel at max pressure to maby blow out the line. sounds like you have very hard watter. try a filter system to stop this for future purposes

Answer 5

if you can find it, put soluble oil in the water system and leave it.all sediment will be cleared in about a week.