How much Sodium Hydroxide needed to raise boiler water pH?

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dogwood

dogwood

Minister of Fire
Mar 22, 2009
825
Western VA
I need to raise the pH of the water in my wood boiler system from 7.0 to about 8.3. I have to treat roughly 1060 gallons contained in the storage, piping, and Solo Innova . I am going to use add Roebic brand pure Sodium Hydroxide (lye) from Lowes to do the job. Anybody know about how much lye I should be adding. I don't know if I should be adding teaspoons or gallons, and can't seem to find any guidance on the net. I'd appreciate any advice.

Mike
 
Glad to see that the pH was not below 7.0. Acidic water is very corrosive.

I did the same thing originally with my system, trial without error given that my chemistry knowledge long ago left me. My technique was to run a circulation pump without the system being pressurized and added lye in doses until pH got to where I wanted it. After each dose I let the pump run for enough time to move the total volume of water, test for pH, add more lye if needed, repeat. The saving grace is that pH of 8.3 is not a magic target. Different mfr's have different recommendations, but after all of my reading on this topic I feel comfortable that pH in the range of 8.0 to 11.0 is OK, with 8.3 being an OK target. So, if you go over some, don't worry, IMO.

Be careful with the lye, protect skin and eyes.

Now, when I moved my entire system from its original install building, an old barn, to my new shop, I used the same company for boiler chemical that Garn uses, and I bought from it the number of gallons of boiler chemical needed to do the job, this time from pH of 7.0 at the start, and then had the company complete a water analysis. This was a bit expensive, but I regarded it worth the cost. The boiler chemical has other components for boiler water protection in addition to pH.
 
jebatty said:
Glad to see that the pH was not below 7.0. Acidic water is very corrosive.

I did the same thing originally with my system, trial without error given that my chemistry knowledge long ago left me. My technique was to run a circulation pump without the system being pressurized and added lye in doses until pH got to where I wanted it. After each dose I let the pump run for enough time to move the total volume of water, test for pH, add more lye if needed, repeat. The saving grace is that pH of 8.3 is not a magic target. Different mfr's have different recommendations, but after all of my reading on this topic I feel comfortable that pH in the range of 8.0 to 11.0 is OK, with 8.3 being an OK target. So, if you go over some, don't worry, IMO.

Be careful with the lye, protect skin and eyes.

Now, when I moved my entire system from its original install building, an old barn, to my new shop, I used the same company for boiler chemical that Garn uses, and I bought from it the number of gallons of boiler chemical needed to do the job, this time from pH of 7.0 at the start, and then had the company complete a water analysis. This was a bit expensive, but I regarded it worth the cost. The boiler chemical has other components for boiler water protection in addition to pH.
Click to expand...
Boiler ph is supposed to be 7 to 8.5
 
Your opinion is respected, but you will find that there is quite a range of acceptable pH. For example, up to pH of 12 is acceptable: http://www.cleanboiler.org/Eff_Improve/Operations/pH_Treatment.asp

There are many other sites with similar information. I recall that my Tarm manual recommended 8.2. The Wood Gun manual recommends 10.5 minimum to 11.0 maximum.

In addition to pH, total alkalinity also needs to be acceptable, the range I have seen in the literature for a hot water low pressure boiler is between 140-700 ppm.

I would not get hung up over a "supposed to" single pH. Talk to your boiler dealer/mfr and follow its recommendations.
 
Thanks for your replies. My Solo Innova manual calls for a pH between 8.0 and 8.6. Jim, when you added doses of lye to your system, about how much lye would each dose contain. Would I dump the whole box of Roebic Drain Cleaner in as a dose, or only a small portion of it. I'm just looking for a ballpark amount to add each go round to get started . I am planning to slowly raise the pH as you did by adding and circulating. I'll check the alkalinity too, as you suggest.

Mike
 
jebatty said:
Your opinion is respected, but you will find that there is quite a range of acceptable pH. For example, up to pH of 12 is acceptable: http://www.cleanboiler.org/Eff_Improve/Operations/pH_Treatment.asp

There are many other sites with similar information. I recall that my Tarm manual recommended 8.2. The Wood Gun manual recommends 10.5 minimum to 11.0 maximum.

In addition to pH, total alkalinity also needs to be acceptable, the range I have seen in the literature for a hot water low pressure boiler is between 140-700 ppm.

I would not get hung up over a "supposed to" single pH. Talk to your boiler dealer/mfr and follow its recommendations.
Click to expand...
Higher PH is prone to scaling.
maple1 said:
7 sounds kind of low. Is there a manufacturer recommending that?
Click to expand...
Says right on cleanboiler.org also over 8.5 and you can have scaling issues. Those manufactures probably don't care if they give out after the warranty is up because than you got to buy a new one.
 
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A blanket statement related to scaling potential is misleading when applied to typical hot water boilers that are low pressure and for practical purposes are sealed, that is, fresh water is not supplied on a regular basis or the boiler water is not regularly drained and refilled. Scaling is usually related to silica in the water, higher pressure boiler systems (above 28 bar), steam generation in the boiler system, and/or admission of makeup water with silica content. None of these are present in low pressure, sealed boiler systems.

I'm not making any objection to pH of 8.5, but I give due note to the Wood Gun recommendation of pH = 10.5-11.0. Maintaining pH at least in the 8 range is important, but I personally would have little concern with pH into the Wood Gun range.

Also important is use of an oxygen inhibitor and alkalinity control. More sophisticated water treatment may include phosphate control and use of polymers and chelant treatment. I assume that the lack of any complaints on this forum of scaling issues with pressurized hot water boiler/storage systems is pretty good evidence that scale is of little concern.
 
... when you added doses of lye to your system, about how much lye would each dose contain. Would I dump the whole box of Roebic Drain Cleaner in as a dose, or only a small portion of it.
Click to expand...
I don't recall exactly, but I do recall not putting in a whole container at once and I did not end up having NaOH (lye) left over from the bottle container I bought at the hardware store, so I must have used smaller doses, mixed the water, tested, and then added as needed.

Edit correction: I did end up with NaOH left over!!!
 
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pH is a log function and it's very easy to move off neutral 7 with very small additions of sodium hydroxide. ...then becomes harder and harder...requiring more acid / base be added as you move toward the extreme ends of the scale.

If you go 'by the book', 1 gram of pure sodium hydroxide (about the weight of a penny) would move 1060 gallons of water from 7.0 to pH 8.8. (then you need about 20 grams to get to pH 10.0) This assumes there is nothing buffering the water...so in reality, you'd add a bit more - but still, we're talking tiny specs of hydroxide vs pounds.

If I had to do it, I'd mix up a 10% sodium hydroxide solution...weigh a 10:1 ratio of water to hydroxide, or at a very rough estimate, I'd say a tablespoon of pellets in a quart of water. Then I'd start adding that solution a few tablespoons at a time. Give it 15-30 minutes to equalize and you should see pH move about 0.2 points with each couple of tablespoons added.
 
Thanks Corey. That's exactly the information I need. I'll mix up a ten percent solution as you suggest. I'm amazed it would take that little Sodium Hydroxide to raise the pH of a thousand plus gallons. Would you, or anyone, happen to know if there are any dangers to the system for using sodium hydroxide in those small amounts. For example, would there be any danger of corrosion to copper pipe which I have in my overheat loop, or to brass fittings, plastic parts, or the bladders inside the expansion tanks for example. I imagine not, but thought I'd ask.

Good advice DaveBP. I emailed Wood Boiler Solutions, Friday, with some questions about their Prep 102 and Treatment Solution 101 products. I was advised to Monday call Mike there for answers. I needed to find out if the Prep Solution 102 would dissolve out excess Rectorseal 5 pipe dope, which I used to on my black iron pipe fittings, clean rust, and be safe to come in contact with expansion tank bladders, gaskets, and plastic parts. And if their Treatment Solution 101 has any impact on pH. I'll post the answers in case anyone else could use this information. And thanks again jebatty.

Mike
 
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