What is best: TSP or just water to clean corroded radiant system

Charlie Taylor_2

The area you mention is black and bumpy just as you see in the photo.

Steve Garson_2

What is best: TSP or just water to clean corroded radiant system

I have radiant heat system heated by a Combicore-II tank. Last month, a new heater was installed to replace a corroded 7-year old original Combicore.

I was astounded by how badly corroded the expansion tank and circulator was. The water was black crud. In the previous four years, I replaced two Taco 007 circulators that were so badly corroded that they seized completely. Now I realized that there must be a connection.

Last year, I installed a Grundfos UPS 15-58FRC with a built in check-valve. I decided to remove this to inspect it last week and saw that it was very corroded in just one year. (See photos). I flushed the system with water and saw how rusty the fluid was. The water is now almost clear, but I am concerned about this corrosion problem. The water temp in the loop runs between 125* and 145* depending on the outdoor temp.

The system has four loops of Onix tubing with aluminum vapor barrier. Everything else is copper except the circulator and the brass valves and the expansion tank. The system has no leaks, since I kept the water feed valve closed. Perhaps the air vent is letting air in? Might the corroded expanion tank had admitted air?

Either way: what is the best way to really clean this system? The spring check valves are still clogging after my flush.

Should I use TSP?

Will TSP hurt the aluminum in the Onix if there is a minor kink or break in the tubing?

Since I can't find the source of Oxygen, should I use some chemical to absorb oxygen?

I figure that the total water capacity of the system is around ten gallons. We're in Boston and the city water is not hard.

Thanks for any help with this. The problem is driving me crazy and my installer hasn't been much help.

Thanks,

Steve

Brad White

I see a handful of issues, Steve

Firstly, if the system were tight, the free O2 would have been driven off and vented away, leaving "dead" water.

(You do have to drive the water temperature up to at least 140F, I would take it to 160+ for an hour or two at least to release this better.)

Any corrosion would be black iron oxide (magnetite) which if anything coats and passivates the remaining metal. You are getting some of that, sure, but I also see red rust which tells me that you have an ongoing fresh water replenishment issue. Solve that first.

You may have a corroded expansion tank but the cycle has to start somewhere.

Are you pumping away? If not, you could be drawing in air on the suction side of the circulator. That may be a source that does not show up as a leak, per se. The expansion tank location is the first thing I would check.

TSP is great for dispersing oils and reducing surface tension of water. You can tell by how "slippery" TSP-laden water feels.

TSP does attack aluminum in concentration when heated. (I have seen it used to dissolve aluminum micro-scale calibration weights to get them to proper weight.) When diluted and flushed to a trace concentration, I see no issue. It will raise the pH a bit, probably a good thing. Tested systems I have done have settled at about a pH of 8.0 to 8.5, 7.0 being neutral. Here in Boston, with Quabbin Reservoir system water, the water tends to be about pH 7.5 or a tad higher.

Cambridge has high minerals, magnesium I think. We all know there is something in their water...

If you really need a cleaning though, TSP is a good start to get any oils out but it will not specifically loosen old crud. It may make the water penetrate better, great.

I would use Rhomar Hydrosolv per their directions, followed by their 922 product for long-term protection. It does include an O2 scavenger and has a shelf-life.

But rule out that leak/make-up issue first.

Hard water is not the issue, free oxygen I suspect is.

kevin coppinger_4

Two things...

call watts...see what they say. They may not want TSP in their tube.
The Rhomar products are very good. In another post you said cost was an issue...but long term you may very well be looking at replacing the system if you don't figure it out...kpc

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Ken_40

Brad's absolutely correct!

Think about this:

Air is definitely entering the system; which is the agent of corrosion. That same air is also exiting the system via a purger or vent somewhere, somehow. Somehow, air is getting into the system, as well as being expelled somehow.

The likely culprits? An air vent is on the suction side of the circulator, perhaps at a high point, perhaps on the near-boiler-piping. The vacuum vs. pressure that must be causing the problem could be air vent based, or simply "on/off" cycling! Vents that let air out while circulation is on (or off)is doing the opposite when the circulator is off (or on).

Remember, even when the system gage says 12 p.s.i., that's only at the gage that reads 12 (or whatever your system reads) - a vaccum could very well exist in the piping (and anything screwed in that area of piping) - near the suction side of the circulator!

As Brad asked, is the circulator pumping "away" from the expansion tank connection point? If so, I'd put the odds at 90% certainty, that is causing the air to be introduced to the system. If no vent is on the suction side of the circ., check the packing nuts on any valves on that side of the circulator.

Please let us know what you find.

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ralman

Just thinking.

How long after removal before the pictures were taken? When I removed some of my piping it only took a few hours time for rust to show up on the parts and pieces from the water and air exposure. Also, is the excessive black iron produced from water velocity that is too high?

Steve Garson_2

The photos were taken ten minutes after removing the circulator

Steve Garson_2

Ken:

You raise an interest point. If you can visualize: the hot water comes out of the tank and then passes a small air vent (similar in appearance to what you would find on a radiator) to a expansion tank to a Spirovent to the circulator and then the heating loop.

ralman

The flange picture.

What is all the black that extends past the surface of the circulator seal? I would think the flange would be clean outside of the seal, around the bolt holes.

Ken_40

?

When you use the term "tank," you are refering tothe expansion tank? Since water cannot come out of a "tank," did you mean "past" the tank connection fitting? Or, did you mean boiler, not tank?

The small air vent. Like a "key bleeder"?

Is not the expansion tank screwed to the Spirovent directly? Or as you suggest, they are in series?



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Steve Garson_2

Ken:

The tank I refer to is the Combicore water heater.

The vent appear to be a Taco Hy-Vent located before in line between the water heater and the expansion tank.

Steve

Steve Garson_2

Best way to add Rhomar products to the system

Just received my Rhomar products to clean the system and then condition the water.

What is the best way to add the chemicals? Should I pick up one of those cheap pumps that goes on a power drill and use a washer hose?

Ken_40

I bought a Teel brand pump

years ago from Granger that cost me ~ $110 way back. I note a bunch of other makers use the exact same utility pump form, implying someone makes it and many brand it as theirs.

It has a c.i. body, 3/4" hose connects on the in and out and comes with two washing machine hoses. Wonderful investment!

I simply took a 5-gallon bucket, put the fluid to be introduced into the pail with a bit of water - already had the sstem cleaned, bled and filled - then opened an entry cock to pump in to, decided how to close something, somewhere to assure full system circulation, found an outlet drain cock somewhere else on the near boiler piping/block - and pumped the concentarted chemical in, while system water went back into the bucket. After five minutes, fully mixed "treated" water came back out and the bucket had exactly what was in the entire system by now - and turned the pump off, threw out the few remaining gallons of over-fill - and knew I had to bleed again, and fireed up the system to free air my work may have introduced.

Making sure to hit at least 160 to drive most air into the air purge point(s).

Voila! The pump has been used many times since, making the 110-dollar investment one of the best ever.

Flooded basement, out comes the Teel. Need fuel oil for the tractor? Out comes the Teel. Pumping out a receiver? Out comes the Teel.

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Charlie Taylor_2

Pump

I just bought a $9 pump that attaches to my power drill. It worked like a charm. I now have the Rhomar Hydrosolv in the system and will see how things look after a couple of weeks. Then we'll add the water treatment to prevent oxygen corrosion and hopefully we won't need a new circulator every two years:)

Unknown

the original combicors failed fairly often I hear; are you sure there wasn't exhange of potable water occurring into the heating system?

scrook_2

Cambridge's water

Cambridge has high minerals, magnesium I think.

It's probably manganese (and perhaps a little iron too).

Charlie Taylor_2

I can not be sure. I think it might be possible. No way to know.