Sludge in Onix?

Geosman

Sadly they said it wasn't possible??? We can confirm it now on a system we did not install but were called upon to service because circuits were not heating as they should. Thick brown "snotty sludge" prevented circulation through floor circuits and plugged up pump check valve assemblies. Once the Tech thought he had the system operating we were back again only to find more debris circulating back out of hidden places and clogging check valves. Had some recent good discussions with Mark Olson at Caleffi regarding biocides and think we have a good test case with this one.

hot_rod

There are a numbers of conditions that can cause systems to sludge. Oxygen ingress is one condition that will cause the ferrous components to corrode, break down and form a black, inky, gritty sludge know as magnetite.

Another type of sludge that appears quite similar to magnetite is caused by an iron bacteria. the bacteria actually lives on the ferrous components in the system and creates a black sludge. Usually the bacteria problem is accompanied by a strong, cotton egg smell to the fluid, similar to sulfur water. I'm told it is actually bacteria "farts"

The best step is to send a fluid sample to a lab, explain the concerns, and let then determine what is causing the sludge. The treatments vary based on the actual cause of the sludge.

It is not uncommon to see the earlier radiant tubes that did not have a O2 barrier to cause sludge formation. Isolating the tube from any ferrous metals is one step, an ongoing chemical treatment is another.

The key is to be able to flush the sludge from all the piping and loops of tube. It may take some time and high velocity flows to accomplish this.

Richard at "Heatmeister" makes a living rehabbing these old non barrier systems in the Summit County area of Colorado, it may be worth hiring him for a consultation.

http://heatmeister.com

Geosman

You are so correct! But in this case the system is all copper with stainless condensing boiler. The only ferrous is in the pump bodies and the bladder tank. The boiler operates for DHW and its intake screens have always been clean. The issue seems to be in radiant tube circuits that sat dormant throughout the summer months. The system is up and running now after flushing each circuit individually using chlorinated city water to force circulation at a much higher pressure than any zone circulator might be able to manage. The task now is to add a biocide to be certain it does not come back.

hot_rod

Still, without identifying the sludge makeup, you are guessing at a solution.

As I recall chlorine did not kill the bacteria we encountered, we tried. I think we used iodine or peroxide, and UV light. We had a professor/ water chemist from the U of Utah involved to identify and prescribe the proper treatment.

Turns out the well driller had the bacteria on his bits and drill rods and was spreading the bacteria to every hole he punched. All his equipment had to be decontaminated also, and some of the well casings he installed.

Geosman

My plan here is to install a bypass strainer dosed with Betadine (iodine) and silver carbonate or nitrate. The combination will reside in the system and prevent any recurrence and the strainer will provide a means to check on system fluid quality. The feed water is from very old (100 yr?) city mains in a neighborhood where lead piping abounds. How it got contaminated is anyone's guess but as Mark H. knows all too well even water heaters and shower heads are not safe when it comes to bacteria growth.