Hydronic 'enhancement'

apg4December 15, 2012

I had to drain down my entire hydronic system to replace a corroded black iron pipe; contact with mortar in a foundation wall did it in - after 70 years....

One of the items being replaced is the auto-fill valve/pressure reducer, which is also toast after 70 years.

Now is there any advantage to any water additives? Corrosion preventers or those that enhance thermal transfer? I'm speaking specifically of "Water Wetter" a product that reduced operating temps in my Land Rover by 10 to 15 degrees. Yeah, it really does work...but in a vehicle with an aluminium block and radiator. And yeah, I'll need a whole bunch more than the pint needed to treat the 2 gallons of coolant....


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Not really needed in a closed hydronic system.

Copper does not corrode all that much, and steel or cast iron corrode until the circulating water has no more oxygen dissolved, then corrosion stops.

It is limited by the oxygen in the fill water being consumed in reactions (and one of the reasons you want to keep the same water as long as you can).

I know one older guy who drains his system when he needs to into a plastic trash can, then uses a small pump and to refill the system.

One of the purposes of antifreeze is also to increas the boiling point of the water-antifreeze mix.
This allows the system to run hotter under pressure.

Residential hydronic systems do not normally run with much more pressure needed than to get water to the highest radiator, and the temp is limited to around 180 F.

The pressure in the boiler at the lowest point is the weight of the column of water in the system, and just a few more PSI usually.

This post was edited by brickeyee on Mon, Dec 17, 12 at 16:28

    Bookmark   December 17, 2012 at 4:25PM
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I would look into measures to ensure air and dirt elimination from your hydronic system.


    Bookmark   December 17, 2012 at 5:21PM
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After a bit of research on-line (and a lot of work under the house) I have learned a few things. As Brickeyee pointed out above, the enemy of hydronic systems (and iron pipe) is dissolved oxygen. Once that's gone, rust can't happen....

First bit learned: Sharkbite fittings are really neat, and a damn sight better than soldering over your head in a crawl space.

For system cleaning and subsequent inhibition treatment, about the only company that deals in consumer-sized chemicals as opposed to tank car quantities, is Rhomar Water Management. Unfortunately, their MSDS literature doesn't list what chemicals are involved.

Last bit: you want the pH of the system fluid to be on the order of 7 to 8.5, slightly basic....


    Bookmark   December 23, 2012 at 3:30PM
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