Somewhat random notes, regarding water pH, Rectorseal Steamaster tablets and cast iron steam boiler.

sbachman7117

This is not really a question and not really verified information... just a list of notes, accumulated as I tried to determine the best stuff to put in my Weil-Mclain EG-45 cast iron steam boiler. Comments, corrections or clarifications are welcomed. My intent is simply to add to the knowledgebase of this very helpful site.
NOTES:

1. EG-45 manual mentions water treatment, but gives very little concrete information (p. 17). Says not to use petroleum-based sealants or cleaners. Indicates that pH should be >7.0.
   
2. Call to Weil-McLain did not yield many specifics regarding any type of additives ("generally not recommended") or specific water chemistry issues, EXCEPT this: water pH should be in the range of 7.0-8.5. Manual only indicates that lower than 7.0 is problematic. The guy I spoke to said that, unlike steel boilers, cast iron boilers can be harmed by high pH water. He suggest I test my boiler water and use baking soda to reduce the pH downward from the 9.3 measured at the water plant.
   
3. Call to Rectorseal tech support did not inspire confidence. The guy I spoke to seemed to indicate that as long as the water turns violet, everything is fine; no need to use anything but City water. I mentioned that my City water pH is 9.3 and that W-M wants 7.0-8.5. I also mentioned what I'd read about their Steamaster tablets, which indicated that they raise the pH. I asked whether the product would adjust the pH in either direction, to hit the 7.0-8.5 range. He seemed to say it would, as long as the water turns violet. My chemistry background is weak, so I don't know whether this is possible, but is seems like a pretty fancy trick.
   
4. When I added Steamaster tablets during the cleaning process, the violet color seemed to simply vary in intensity in direct proportion to the level of dilution. The bottle says "color coded for accurate dosage", but I did not notice any distinct color change at a particular dosage. More tablets=More color. More water=Less color. The instructions do not indicate what shade of violet is "correct."
   
5. Although I had read that de-mineralized water would be best, I also read that it is actually corrosive. The chemist at the Ann Arbor Water Dept. shared that view. He said that the "purified water" available locally is not well defined and he had no specific bottled water recommendation. Same with the engineer at Weil-McLain, who listened to some of the chemical analysis report for my City water and said it should be okay, as long as I adjust the pH into the 7.0-8-5 range.
   
6. 
   

KC_Jones

@ChrisJ I seem to remember you doing some experimentation with the steamaster tablets? Perhaps a link to that thread would help out the OP. I also use the tablets, but Chris has "played" with them more than I.

SlamDunk

If your city's water supply's ph is 9.3 (sounds high, really high-14is highest) you should be adding acid to bring it down. Not baking soda, baking soda raises ph-or rather neutralizes acidity which is any number lower than 7; 1 is lowest.

Also, adding too many tablets will make your boiler water sudsy and cause surging which will cause short cycling. Ask me how I know!

However, the water WILL be a pretty purple.

I would double check with your city if I were you. The numbers from their water quality report should be online. I beleive the pH target range is 6.2-8.5.

ChrisJ

Cast iron having problems with a high PH is news to me.
If it was mine I'd be perfectly content with a PH of 9 to 10 but I'm not an expert either.

Best thing I could find quickly was this. Can't really search too much on the subject right now.

http://www.grundfos.com/service-support/encyclopedia-search/cast-iron.html


Various types of cast iron are widely used in industry, especially for valves, pumps, pipes and automotive parts. Cast iron has good corrosion resistance to neutral and alkaline liquids (high pH). But its resistance to acids (low pH) is poor.

ChrisJ

And this.

http://www.cleanboiler.org/Eff_Improve/Operations/pH_Treatment.asp

Caustic Attack

Caustic attack on boilers is a localized attack due to extremely high pH (12.9 +). It can take two forms: caustic gouging or caustic cracking, also called caustic embrittlement. Caustic attack or caustic corrosion, is often encountered in phosphate treated boilers in which deposits of phosphates or other 'scale' occur in high heat transfer areas. Boiler water can permeate the porous deposit resulting in localize corrosion. When it is coupled with significant heat flux, concentration of the boiler water occurs rapidly speeding the corrosion.

Jamie Hall

If it were my boiler, I'd double check the pH of you city water -- as someone said, a pH of more than 8.5 is a wee bit unusual -- and, frankly, if it were in the proper range -- 7 to 8 -- I'd leave it alone.

Deionized or distilled water is remarkably corrosive; you really don't want to use that.

In terms of chemistry, what you want is low to moderate total dissolved solids and proper buffering to hold the pH in the 7 to 8 range, and city water should be doing that.

ChrisJ

Jamie Hall said:

If it were my boiler, I'd double check the pH of you city water -- as someone said, a pH of more than 8.5 is a wee bit unusual -- and, frankly, if it were in the proper range -- 7 to 8 -- I'd leave it alone.

Deionized or distilled water is remarkably corrosive; you really don't want to use that.

In terms of chemistry, what you want is low to moderate total dissolved solids and proper buffering to hold the pH in the 7 to 8 range, and city water should be doing that.

My sister's city water is something like 10 or 11. They have a hell of a time dealing with their swimming pool. The water co told them it comes from a well and it is what it is.

But their 30 year old boiler isn't complaining.

SlamDunk

forget their boiler. you should be more concerned with their toilet.

I was reviewing ph scales and learned that milk of magnesia also has a ph of 10

ChrisJ

SlamDunk said:

forget their boiler. you should be more concerned with their toilet.

I was reviewing ph scales and learned that milk of magnesia also has a ph of 10

Really not going there....
I haven't had my dinner yet.