Helping daughter with new to her 2005 boiler water issue

Cudavid · September 22

hello and thank you all for your time! Domestic hot water boiler, 2 zone.

Noticed a 2 quart bucket under pressure relief and had some water in it, black, with sediment. Son in law said he empties a few times a year. Hmm, so I popped relief valve a few times to see if sediment on the seat, took a few tries, then sealed. Water was black and appears to have sediment.Notices the automatic air vent on top of air scoop is well stained from leaking. Air bladder has 12 psi and is not water logged

My question, should I flush boiler? Is the water condition normal? Are the details sufficient to offer possible big picture on cause/ effect? I know air in system accelerates corrosion? Could a few years of a defective air bleed cause the dirty water?

Thank you

hot_rod · September 22

What type of boiler? Is it connected to any infloor radiant tube? Does it have an autofill valve? Is it a combined radiant/ DHW system?

Black deposits or sludge is often times magnetite. This forms when ferrous metals in the system break down. Which happens if oxygen is entering the system, non barrier radiant tube for instance. Or a small leak caused fill water to enter occasionally.

A seeping relief could be an indication of a failed expansion tank.

Hydronic water rarely stays clear, a slight to dark grey is normal from water touching ferrous metals. Black or red water= oxidation happening.

Yes a flush will help, once you determine a cause. A hydronic cleaner will dissolve any sludge and flush it out. Plain water will not do much.

mattmia2 · September 22

normally i'm a dripping relief valve probably means a bad/uncharged expansion tank or not holding prv or leaking dhw coil but in this case if it is just a little bit in a bucket over a year it is probably just a bad relief valve. The auto air vent is also probably bad, either needs cleaning or replacement. They eventually will leak and need attention.

The black water at the relief valve may just but oxide that collected at the valve. Is water from a drain valve also like that?

What is the pressure of the boiler cold and hot? If it is 12-18 psig or so and stays in that range cold and hot it is probably just some worn out parts.

Cudavid · 1:09AM

hi and thank you, for quick feedback, unsure of brand will get, no in floor radiant, there are two zones that use air het exchangers too heat the house. I will get the brand and model.

It does have a . Domestic HW coil and Storage tank. Has a 30 Psi relief valves, running at 12 psi when hot, yes there is an automatic add water valve.

I ran at least 2 quarts of water from presssure relief valve, water did not appear 5o change , stayed very dark. I did not look for/ or test the drain valve.

Tapped on expansion tank top 1/4 above bladder is full, lower sounds hollow and pressure is 12 psi, so seems ok? Other test I should do?

Again, thank you

hot_rod · 1:44AM

if there is a drain at the bottom of the boiler, drain a glass full of, let it sit overnight

If there is black sediment after it sets for 8 hours take a magnet and stick it against the glass

If the sentiment attracts to the magnet it is magnetite

When a sealed closed loop system is first filled the O2 in the H2O will come in contact with with ferrous metals , pumps, pipes, expansion tank etc.

A small amount of oxidation occurs, some grey coatings appears on ferrous parts

The O2 is consumed and you have “dead” water, water starved of oxygen

The system will stay in that condition unless fresh water is added, or oxygen enters

Any plastic tubing in the system? Oxygen can migrate through pex tube

The higher the system temperature the higher the potential ingress of O2

close the fill valves and see if the boiler pressure drops over a few days That rules out a leak

Helping daughter with new to her 2005 boiler water issue

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