Search with Wattson

Notifications

Clear all

Joining the Renewable Heating Hub forums is completely free and only takes a minute. By registering you’ll be able to ask questions, join discussions, follow topics you’re interested in, bookmark useful threads and receive notifications when someone replies. Non-registered members also do not have access to our AI features. When choosing your username, please note that it cannot be changed later, so we recommend avoiding brand or product names. Before registering, please take a moment to read the Forum Rules & Terms of Use so we can keep the community helpful, respectful and informative for everyone. Thanks for joining!

DIY powerflushing tutorial

bobflux · 2026-10-03T20:53:06Z

Over the years, due to the non barrier PEX underfloor heating installed by the previous owner, the ancient cast iron boiler has turned into rust and sludge which has deposited inside the UFH loops... time to clean the mess. This contraption mixes water with compressed air and injects it: The water inlet is taken before the house's pressure regulator, so it comes in at 7 bar, which compensates for the pressure drop in the red PEX pipe. With only 3 bar supply it would have been necessary to use 20 or 25mm pipe to get proper flow. It is followed by a 4-way valve to allow flow in both directions. Besides the compressor (which I already had) and the flex hoses (which came out of the old heating system) this is not expensive to implement. Probably less than €100. It worked wonderfully. It pulled a ton of crap from the loops. Compressed air helps a lot. I rinsed with with water until it came out clear, then turned on the air: brown stuff immediately came out, and kept coming out. I let it run for several hours, reversing flow direction every five minutes, one UFH loop at a time. Air bubbles create a sort of water hammer effect which works really well for dislodging crap. Also air flows through pipes easier than water, so an air/water mix can flow at surprisingly high speeds through UFH loops, several meters per second at least. I used a feed pressure of 2.5 bar. Drain pipe must be firmly secured. It did its best to get out of the washing machine U-bend. Once this is done, it's time for chemicals. I got a 200l polyethylene bin from a local farmer, and reused the filter and pump from the old groundwater heat pump system. The previous contraption is now partially disassembled, keeping only the air injector. UFH loops are flushed with compressed air, then the bin is first filled with Sentinel X-800 cleaning agent diluted to spec in 40°C water, then the pump turned on. Again, reverse flow every five minutes and do each UFH loop in turn. Feed pressure at the pump outlet is 3-4 bar depending on length of UFH loop being cleaned, flow is 2-3 m3/h water plus air, so velocity in the UFH loops should reach 5-10 m/s. The whole thing is shaking and kicking. Water came out clear at the previous step, but the cleaning agent still pulled a lot of crap out of the pipes. These flakes are quite large (the fitting is 1" for scale), I wonder how that got through the circulator... Well, it died, maybe that has something to do with it... This is what the filter caught: ...I only put the filter in line when I switched from plain water to Sentinel cleaning agent, so who knows how much of this stuff got flushed into the sewer. Some of these flakes are large enough to match the internal diameter of the UFH pipes, I guess the compressed air helped break them up. Next, I rinsed with clean water plus air. The reverse osmosis rig is currently filling the big blue tub with demineralized water, so tomorrow I'll pour some inhibitor in it and use the pump to flush and fill the loops. Conclusion: I'm very happy with this DIY powerflushing stuff. It makes a mess of course, but I save 5-800€ per manifold, and I have 3 of these manifolds. Not bad for assembling a bunch of fittings, setting a timer to switch valves every five minutes, and mopping the floor afterwards.

Page 2 / 2 Prev

DIY

Last Post by Transparent 9 minutes ago

15 Posts

5 Users

5 Reactions

759 Views

RSS

Transparent

(@transparent)

Illustrious Member Moderator

Joined: 5 years ago

Posts: 3461

12/11/2026 2:13 pm

Ah! So it's the electrochemical series which drives the Crud Cycle:

What am I not understanding in that comment from @pirate-rich about System Inhibitor increasing conductivity? 🤔

This post was modified 45 minutes ago by Transparent

Save energy... recycle electrons!

ReplyQuote

bobflux

(@bobflux)

Reputable Member Member

Joined: 9 months ago

Posts: 207

Topic starter 12/11/2026 2:31 pm

Inhibitor contains ions which increases conductivity no matter what the ions are... The only water without conductivity would be ultra pure deionized water. But then, you'd also need to remove the oxygen before filling, so it's a never ending headache.

The real killer is oxygen getting into the circuit.

Where does that crud cycle pic come from?

This post was modified 32 minutes ago by bobflux

ReplyQuote

Transparent

(@transparent)

Illustrious Member Moderator

Joined: 5 years ago

Posts: 3461

12/11/2026 2:55 pm

The Crud Cycle diagram was created here during my lunch break 😊
Creativity occurs when I'm feeling less inhibited.

I was just attempting to put my previous question into graphical format to aid understanding.

It's unclear whether @pirate-rich was recommending that we don't use System Inhibitor...
... or perhaps stumbling across a new design of battery, in which we store the energy in our corroding pipework!

Save energy... recycle electrons!

ReplyQuote

Page 2 / 2 Prev

Forum Jump:

Previous Topic

Currently viewing this topic 2 users ( bobflux, Transparent ) and 4 guests.

Recently viewed by users: JamesPa 41 minutes ago.

27 Forums
2,815 Topics
66.7 K Posts
2,589 Online
7,230 Members

Forum Icons: Forum contains no unread posts Forum contains unread posts

Topic Icons: Not Replied Replied Active Hot Sticky Unapproved Solved Private Closed

RE: DIY powerflushing tutorial

The Crud Cycle diagram was created here during my lunch...

By Transparent , 9 minutes ago
RE: Power cut and no heat

@brazilguy67, glad you've managed to get someone to hav...

By Mars , 11 minutes ago
RE: Air source heat pump roll call – what heat pump brand and model do you have?

We've had an influx of new members joining the forums o...

By Mars , 1 hour ago
RE: How Can I Prove Coal Was My Main Heating Source Without Receipts?

Got excepted for the grant now so thanks for the replie...

By Chilli304 , 3 hours ago
RE: Numerous issues – Onecta shows Climate control “INACTIVE” with ! icon – fixed by rebooting the Wireless GatewaykW Daikin Altherma 3

Daikin Altherma 3 R F+W, room thermostat control, weath...

By JanHarley , 4 hours ago
RE: Buffer tank on a 2 x 14kw Ecodan system

Pretty much as I had guessed in my crude scaling from m...

By JamesPa , 7 hours ago
RE: Help me keep the faith with my air source heat pump installation

Well you have a vibration generator running at some fre...

By bobflux , 20 hours ago
RE: Why don't people choose heat pumps?

@susannasaunders The link I have found may provide a li...

By Toodles , 22 hours ago
RE: Who's your electricity provider and what's your tariff?

@downfield Thats a decent rate, I’m shocked they hadn...

By Papahuhu , 2 days ago
RE: Should Households Who Can Afford It Pay More for Energy to Help Those Who Can't?

@batpred I mentioned earlier that targeting the payment...

By Toodles , 2 days ago
RE: Adventures in heat loss calculations

@toodles thanks! So as suspected, around a doubling of ...

By SusannaSaunders , 2 days ago
RE: Books about heat pumps

Six books in three years and I think I’ve now covered j...

By Mars , 2 days ago
RE: Grant Aerona3 13kw - Buffer Tank - Heating Journey

@heymikey Well done in achieving as nearer a match acro...

By Toodles , 2 days ago
Grant Aerona - Weather Compensation and Schedules

Im trying to set up a friends Grant Aerona. The WC curv...

By bontwoody , 3 days ago

Renewable Heating Hub Heat Pump Forums

DIY powerflushing tutorial

SPONSORS

Join Us!

Installer Finder

Degrees of Separation

Latest Posts

SPONSORS

Members Online