OT: acid to clean scale in boiler system

I have a booster tank plumbed into the coil of my oil fired boiler, a circulating pump constantly keeps the tanks water up to temp. Can I run
muriatic acid in this closed loop to de-scale it. I have done this to just the coils of other boilers before but am wondering if the bronze circulating pump or anything inside the hotwater tank will be negatively affected. How can I tell when the scale is totally removed and how much can I dilute the acid before it becomes useless. Can this also be run throught the heating system.
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wrote:

I don't think that bronze would be very hapy about muriatic acid! The usual kettle/coffee-pot descaler is acetic acid, essentially real strong vinegar. Another cheap acid used for de-scaling is citric acid, which is also known as vitamin C.
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I am pretty sure tha "CLR" the common descaler has phosphoric acid in it

just
circulating
How
the
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wrote:

And don't they use oxalic acid in rad cleaners?
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brought forth from the murky depths:

Newp, just glycolic, sulfamic, and citric acids.
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Partly right, the bronze would not like it. Citric acid is good for iron oxide scale but not for calcium/magnesium based scale which is usually the problem in boiler heat exchange. BTW, vitamin C is Ascorbic Acid. Use INHIBITED hydrochloric and follow the directions. Isolate the tubes from the bronze pump & use a cheap sump pump like a little giant. Check acid strength with a basic titrant and cehck every few minutes. Strength should go down as acid is neutralized. 2 tests in a row with no strength change, drain, flush & neutralize with caustic. Do not clean with the boiler hot! You should start with about 4-5% acid strength. Greg Sefton
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On 02 Feb 2004 19:42:32 GMT, snipped-for-privacy@aol.com (Bray Haven) wrote:

How is hydrochloric acid inhibited?
Just curious
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wrote:

It doesnt like to be seen nude.
Gunner
The two highest achievements of the human mind are the twin concepts of "loyalty" and "duty." Whenever these twin concepts fall into disrepute -- get out of there fast! You may possibly save yourself, but it is too late to save that society. It is doomed. " Lazarus Long
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Gunner wrote:

Not even at " halftime " ? ;-) Ken Cutt
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I like Gunner, et al's reply better but here's mine. HCL can have inhibitors in it that reduce the attack on various metals. It won't protect them entirely, as I've seen total systems dissolved using inhibited acid. One inhibiting ingredient used is (IIRC) Rodene for ferrous metals and another is tolytriazole for cuprous metals. Check your HVAC or industrial water treatment company for these. Greg Sefton
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Bray Haven wrote:

I'm not a chemist - however molar value (IIRC) is the stuff.
simply said - if it is dilute - it is inhibited. Use limited ionic extraction due to lower count. I suspect there are some gels that limit ionic flow and keep the concentration up. Something to look up on the web.
Martin
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I don't think that bronze would be very hapy about muriatic acid!

Vitamin C is ascorbic acid. Not citric acid. Any of them would work here but citric is less expensive i think. Muriatic acid as mentioned is not such a pleasure to work with, but it will be quicker. HCl will be a problem if you get any vapours out in the room. My bathroom mirror never looked ok after I had an open bottle of HCl in the bathroom. If (when) I will do the operation I would go for citric acid. As for the suggestion of siphoning HCl by mouth I say dont do it! You might be careful and not get it in your mouth, but what if you misses and do get a mouthful? Use a selfstarting siphon. I have one for pumping gasoline. Henning
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The times I did just the coils I set up a system such as the one Don Wilkins mentioned but I rented a waterbed pump to continuously run the acid throught the coil. Apparently these little pumps suffer no ill effects from the acid, I was told this by a few different plumbers. As I remember the fumes were unbareable, I thought I was going to die until I made it outside. I figured it must have been chlorine gas released from the HCL. Since then I learned to put a fan in the basement window blowing out and open a window on the opposite side of the house to allow for proper ventalation.
wrote:

but citric is less expensive i think.

will be quicker.

mirror never looked ok after I had an open bottle of HCl in the bathroom.

might be careful and not get it in your mouth, but what if you misses and do get a mouthful?

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As I remember the fumes were

Actually HCl is in itself a gas. It is dissolved in water to get the usual liquid acid. So if you sluch it arround its not so hard to release some of the gas. Not as bad as chlorine gas, but still not very funny to breath. Henning
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wrote:

I believe I had a similar hot water system. My furnace had a copper coil which was heated by the hot water in the furnace boiler section.
I made a few plumbing modifications to the system so I could isolate the heat exchange coil from the rest of the domestic hot water system. This was simply a couple spigots and valves. Three 5 gallon plastic pails, and some transparent Tygon tubing completed the apparatus.
When it was time to sluice out the deposits in the heating coil I closed off the valves thus isolating the domestic water system. There were two plugs to remove and now I had a clear path through the heating coil.
I put a plastic hose connector on each of these openings with one hose reaching down to the floor and the other hose reaching about three feet above the furnace. Now I placed a plastic bucket on top the furnace and secured the plastic hose so it would reach to the bottom of the bucket AND stay there. At this point you should see where we are heading. :-)
Add enough 10% muriatic acid so the top bucket is about 3/4 full. Start the syphon by sucking on the hose that goes to the floor. You should be able to watch the acid flow in the upper hose so you don't get a mouthful. Once the syphon starts place the lower hose in a second plastic bucket.
When the bottom bucket is about half full transfer the hose over to the third plastic bucket and dump the contents of the lower bucket to the top bucket. This keeps the syphon running until you get tired of lifting the third pail.
When the acid comes through without bubbles (carbon dioxide) you have cleaned the coil. If the furnace is at temperature the cleaning may take less than 2-3 minutes. Dump the acid and rinse with water until the acid is eliminated. I am a chemist and test by dipping my finger in the water and tasting. Your procedure may be different but you will run quite a bit of water through before you try the taste test.
No pump in this method but muriatic acid only dissolves the surface zinc from brass leaving a copper surface so any brass fitting will be OK.
An aside: As a young chemist I quickly learned to never leave a cup of coffee unattended in the lab. It was an absolute guarantee that someone would give it a small shot of HCl from a squirt bottle. I will guarantee from experience that if you don't rinse well your coffee will taste awful.
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