Constant sludge

[Jessh30]

Hi, hoping someone can help!
We moved into our new build in 2021, within a few weeks our ideal combo boiler showed an FU error code, we had power flushes etc every couple of months for the first couple of years living here. We tried to argue with developers/installers but no one would take on the costs & said they didn't know what was causing the issues.

Fast forward to now, we had a new boiler fitted June last year due to the contact damage caused by build up in the system (see pictures), we have already had to have one power flush on the new boiler and now we have just had another FU error code & the hot water is starting to go cold.

We've had numerous plumbers out over the years, loads of power flushes and no one can seem to get the bottom of why it is happening.

We are now out of pocket after numerous call outs & a brand new boiler!!

Hoping someone could give us some answers as to why the power flushes aren't working? Or working for a few weeks/months at a time.

It's underfloor heating throughout the house.

Pictures below are from other houses on oir road who have had similar issues, now a sludgy looking substance comes out after flushes

 

[omph]

What is the colour of the sludge ? Do you have any design files for the underfloor heating layout ? how many zones do you have ? How do you use the underfloor heating ? Do you have radiators, and are they also taken off and manually flushed ? Does the boiler return have a magnetic filter ?

Also, how hard is your property water ? and how much inhibitor is being used ? It will need to be calculated, and tested - not just flung in.

P.S. you also need to be wary of bacteria overgrowth when dealing with low-temp heating systems - so underfloor heating means you should have a biocide if using tap water.

 

[OvertonPlumber]

Non barrier pipe used?

 

[Johntheo5]

If its a sealed system and doesn't require frequent top ups or any leaks arn't masked by a auto make up PRV then bacteria could be the problem, get the water tested.

 

[omph]

Non barrier pex is a plausible cause considering companies cut corners for new builds to save money.
I think the best solution provided no leaks is to powerflush (that includes doing each radiator individually), remove all water from the system and refill with de-mineralised and degassed water - no inhibitor or biocide required. For demineralisation use purotap micro or leader - If using micro you should get two units and chain them so the water is filtered twice before entering the system. You can also install an Elysator trio unit that will inline de-gas the system whilst also having a sacrificial anode and other cool features.