# descaling commercial big heaters



## Protech (Sep 22, 2008)

I don't do much commercial but I just received a call from a hotel about their AO smith cyclone Xi heaters. They are BTH 250 models and they have not been descailed yet. They are about 2 years old and the water is quite hard in this area.

Questions: 

What deliming solutions would you recommend?

How long does it usually take to delime once onsite in front of heaters with tools in hand per heater?

How do I get the coil clean? Filling the whole tank with solution seams very slow and would use quite a bit of cleaning solution. Maybe a flexible sprayer wand?


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## ckoch407 (Sep 30, 2009)

Protech said:


> I don't do much commercial but I just received a call from a hotel about their AO smith cyclone Xi heaters. They are BTH 250 models and they have not been descailed yet. They are about 2 years old and the water is quite hard in this area.
> 
> Questions:
> 
> ...


Ive never done a cyclone but I have done some of the old copper coil, brass fin, and storage tank ones. I think it was Calci-Solve, and Ive heard of people using Clobber with a proper dilution. I would go online and double check the manuals though.


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## Protech (Sep 22, 2008)

Will Calci-solve or clobber damage the lining?

I was just reading about "rydlyme". Seems like a good choice. The only thing I'm unsure about is how to clean the big coil that is way above the hand hole. I was thinking about those hand pumped sprayers that the pest control guys use. I could just bend the pole that goes to the sprayer so that it could reach up into the tank and spray the coil off. What do you think?

I suppose I could just fill the whole tank with a diluted solution but that would take a long time and use a whole lotta chemicals. Maybe pour in a few gallons on concentrated solution thru the hand hole. Then pump in RO water from some pre-filled trash cans to dilute. That way it gets everywhere. Seems like it would take a long time and they do NOT want lots of down time. The heaters cannot be drained separately as there are no isolation valves on the outlet manifold, only the inlet.

go online and double check the manuals though.[/quote]


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## ckoch407 (Sep 30, 2009)

Protech said:


> Will Calci-solve or clobber damage the lining?
> 
> I was just reading about "rydlyme". Seems like a good choice. The only thing I'm unsure about is how to clean the big coil that is way above the hand hole. I was thinking about those hand pumped sprayers that the pest control guys use. I could just bend the pole that goes to the sprayer so that it could reach up into the tank and spray the coil off. What do you think?


[/QUOTE]

Not sure bout the cyclones, but thats what the manual used to recommend... filling the tank with diluted hydrochloric acid for those dinosaurs. It probably would do damage if you sprayed it right on the coil. Bad comparison on my part... apples oranges.


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## Protech (Sep 22, 2008)

They want to sell me their proprietary "un-lime" solution which is special order and they charge a premium.

Do you think it would hurt the lining if I just filled the tank with hydrochloric acid diluted with RO water 1 parts to 5 parts and then kicked the burner on until the solution was about 120F? The tanks heat to that temp in about 5 minutes.

Not sure bout the cyclones, but thats what the manual used to recommend... filling the tank with diluted hydrochloric acid for those dinosaurs. It probably would do damage if you sprayed it right on the coil. Bad comparison on my part... apples oranges.[/QUOTE]


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## 1703 (Jul 21, 2009)

Going from memory here.....

AO Smith wants the anodes pulled before deliming

If you pull the access cover, have a new gasket, new bolts, drill and tap handy.....


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## SewerRatz (Apr 25, 2009)

The reason they want the anode rods pulled before deliming a heater is the acid used to delime the heater and the magnesium anode rod will produce large quantity of hydrogen.

Unlime is the best out there, it uses phosphoric acid (same stuff in soda pop) and washes out of the heater easily and does not do any damage to the heater or pipes.

The local supply here sells Unlime by the gallon for 25 bucks if I recall might be a bit more than that. It has been a while since I priced the stuff. It is cheaper to get it in the 5 gallon jug though.


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## Protech (Sep 22, 2008)

Why not just phosphoric acid? The problem with these heaters is that they have a spiraled flame tube that is up high above the hand hole. I can scoop the scale out of the bottom but the stuff stuck to the flame tube is not easily accessible. The anodes are DC powered anodes and do not need to be removed during deliming. These heaters are only about 2 years old so they shouldn't be too bad.

I think the thing to do here is sell them some isolation valves on the outlets so that each heater can be isolated and drained individually. That way I can just truck in 2 55gal drums of RO water and a few gallons of phosphoric acid. I can just mechanically remove most of the scale and then fill the heater up with the RO water/phosphoric acid mix and let it sir for a day. Come back the next day and do it all over again with the next heater.

What do you think?


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## Farmtek (Feb 8, 2010)

That rydlime is a good product that works.


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## SewerRatz (Apr 25, 2009)

Protech said:


> Why not just phosphoric acid? The problem with these heaters is that they have a spiraled flame tube that is up high above the hand hole. I can scoop the scale out of the bottom but the stuff stuck to the flame tube is not easily accessible. The anodes are DC powered anodes and do not need to be removed during deliming. These heaters are only about 2 years old so they shouldn't be too bad.
> 
> I think the thing to do here is sell them some isolation valves on the outlets so that each heater can be isolated and drained individually. That way I can just truck in 2 55gal drums of RO water and a few gallons of phosphoric acid. I can just mechanically remove most of the scale and then fill the heater up with the RO water/phosphoric acid mix and let it sir for a day. Come back the next day and do it all over again with the next heater.
> 
> What do you think?


UnLime is 99% phosphoric acid. So I do not see an issue.


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## PaulW (Jul 31, 2008)

Sub it out to us We are the AO Smith state reps! Yes on the Un-lime.
Paul


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## Protech (Sep 22, 2008)

How much to do one heater?
How much for an ignitor?



PaulW said:


> Sub it out to us We are the AO Smith state reps! Yes on the Un-lime.
> Paul


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## PaulW (Jul 31, 2008)

> How much to do one heater?
> How much for an ignitor?


To do one heater in a perfect world where the room is water resistant roughly $245.00 includes new gasket.

For one ignitor installed $214.00 

Paul


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## Protech (Sep 22, 2008)

The room has a floor drain 3 feet away from the heaters. 

At those prices I would prolly sub it out. I think I was quoted something like $125 just for the ignitor plus shipping and tax.

I just don't see how you can pay to drive out there, drain the heater down, pull the access, manually remove the scale, then treat the flame coil (chemical costs), supply and install a new gasket, fill the thing back up and test fire it all for $245.



PaulW said:


> To do one heater in a perfect world where the room is water resistant roughly $245.00 includes new gasket.
> 
> For one ignitor installed $214.00
> 
> Paul


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## Tommy plumber (Feb 19, 2010)

Why are you looking to de-scale W/H? Don't you want them to fail so you can replace them? :laughing:


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## ROCKSTARPLUMBER (Dec 14, 2008)

This thread will be useless with out pics of the work Ken. Hope you get the job. Look forward to some pics.


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## Protech (Sep 22, 2008)

I'll post some another day


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## PaulW (Jul 31, 2008)

> I just don't see how you can pay to drive out there


Where is out there?

Paul


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## TheMaster (Jun 12, 2009)

PaulW said:


> Where is out there?
> 
> Paul


 
I think he means anything that is not on the street where his office is located.....anything past that point is "Out there". But he could mean anything outside of his garage I wouldn't even touch it for 245.00 so I know he wont down in central FL.


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## Protech (Sep 22, 2008)

*Just a thought*

How much calcium carbonate does RO water dissolve at room temperature? I know that acid neutralizers for well systems use calcium carbonate and the chemical must be replenished as it is dissolved away by the acidic water. I was just wondering how practical it would be to use RO water to descale a boiler. 

Let’s say hypothetically that 1 gallon of RO water at room temperature will dissolve 5 grams of boiler scale. That would mean that you would need only 200 gallons of RO water to dissolve a kilo of boiler scale.

Why does this matter? Well, what if a small RO unit could be installed in a boiler room with flush rigs built into the boiler piping. When one of the boilers starts popping you simply turn the isolation valves off to 1 boiler and open the RO purge valves and walk away. Come back a few days later and all of the scale will be dissolved away. Switch to the next boiler and repeat. Once said rig is installed, boiler maintenance is cheap.

Thoughts?


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## Protech (Sep 22, 2008)

From Wikipedia: _"Water with a pH maintained to 7 can dissolve up to 15.9 g/L of CaCO3"_


Thinking out loud: 15.9 g/L means 62.89 L is needed to disolve a KG of boiler scale. So if I have an estimated 2.5 kilos of scale I want to get rid of I will need 157.23 L of RO water or about 41 gallons of RO water. 

Seems like if this works the way the math says it does, I would be better off just filling up some barrels of RO water and trucking them in rather than buying chemicals. 

Thoughts?


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## PaulW (Jul 31, 2008)

I think your spot on flushing the system with RO especially the one in question only two years old would work beautifully. Most systems have the Culligan system (or equal) in place. 

Paul


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## ckoch407 (Sep 30, 2009)

Protech said:


> How much calcium carbonate does RO water dissolve at room temperature? I know that acid neutralizers for well systems use calcium carbonate and the chemical must be replenished as it is dissolved away by the acidic water. I was just wondering how practical it would be to use RO water to descale a boiler.
> 
> Let’s say hypothetically that 1 gallon of RO water at room temperature will dissolve 5 grams of boiler scale. That would mean that you would need only 200 gallons of RO water to dissolve a kilo of boiler scale.
> 
> ...


When you say boiler do you mean a real boiler that makes steam or direct systems for heating water? The theory sounds pretty good if it works. If you invent something don't sell out cheap. But on real boiler systems all of the ones I've ever seen have a softener on the make up water inlet. Nothing for big direct heaters though.


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## Protech (Sep 22, 2008)

I'm talking about a big direct water heater. BTW, I'm pretty sure that even a direct water heater that is 250 gallons or more is technically a boiler even though it doesn't actually boil water.

Also, I believe I did say that they were AO Smith Cyclones.



ckoch407 said:


> When you say boiler do you mean a real boiler that makes steam or direct systems for heating water? The theory sounds pretty good if it works. If you invent something don't sell out cheap. But on real boiler systems all of the ones I've ever seen have a softener on the make up water inlet. Nothing for big direct heaters though.


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## Protech (Sep 22, 2008)

Well, I can't sleep so I figure I'll post some pics.


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## SewerRatz (Apr 25, 2009)

Protech, it may not be pictured, where is the vacuum relief valve? Or is it not required per your code?

Code for us is if the heater is elevated, or bottom feed it requires a vacuum relief valve.


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## Protech (Sep 22, 2008)

no vacuum relief. I don't believe it is required here. I almost never see them.

Yes, I understand what it's function is.




SewerRatz said:


> Protech, it may not be pictured, where is the vacuum relief valve? Or is it not required per your code?
> 
> Code for us is if the heater is elevated, or bottom feed it requires a vacuum relief valve.


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## Protech (Sep 22, 2008)

Well I got the job :thumbup:

I'll post some pics soon.


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## Pipe Rat (Apr 5, 2009)

Protech said:


> From Wikipedia: _"Water with a pH maintained to 7 can dissolve up to 15.9 g/L of CaCO3"_
> 
> 
> Thinking out loud: 15.9 g/L means 62.89 L is needed to disolve a KG of boiler scale. So if* I have an estimated 2.5 kilos* of scale *I want to get rid* of I will need 157.23 L of RO water or about 41 gallons of RO water.
> ...


How much?:laughing:


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## Protech (Sep 22, 2008)

I got 2.5 kilos of white crystaline to get rid of man. You buyin?:jester:



Piperat said:


> How much?:laughing:


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## Protech (Sep 22, 2008)

So I tried an experiment today. I tried some concentrated sulfuric acid (drain opener) on an old gas water heater. The idea is to use an acid that is less costly than phosphoric acid to drop the PH and dissolve the calcium carbonate. The problem is that the sulfuric acid was so strong that it ate the enamel lining right off the tank and started dissolving the tank walls. It the sulfur also reacted with the boiler scale and formed insoluble sulfate salts which was the opposite of what I was hoping for.

I wonder if I dilute the acid with a bunch of RO water, maybe it will up the PH enough so that the liner doesn't dissolve. Also, maybe the lower TDS will keep the sulfate salts from forming.

I'll post the results of the next test.

It would be nice if I could get this to work as sulfuric acid is like 1/4 the cost of phosphoric acid.


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## cbeck (Mar 7, 2012)

Protech, what were your final results for this job?


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## Protech (Sep 22, 2008)

I used RO water to dilute hydrochloric acid. circulated in the boilers for about 1/2 hour and drained them. Flushed with potable water until the PH went back to 8. Worked perfectly.


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## cbeck (Mar 7, 2012)

Protech said:


> I used RO water to dilute hydrochloric acid. circulated in the boilers for about 1/2 hour and drained them. Flushed with potable water until the PH went back to 8. Worked perfectly.


What were your ratios?


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## Gettinit (May 9, 2012)

I hope others know that you are supposed to use a NSF 60 approved solution.


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## Protech (Sep 22, 2008)

cbeck said:


> What were your ratios?


I think it was 1 gallon of muriatic acid to 40 gallons of water. 

You can just get the ph down to 5-6 and hold it there by adding acid and rechecking ph periodically.

Powered anodes can stay in but galvanic anodes must be removed before adding acid.


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