Preventing Boiler Corrosion

Fishin_Rod

The original boiler in our house (1918) lasted 92 years before dying of severe corrosion. The replacement boiler only lasted one year before a cast iron end section rotted out. The installer replaced it under warranty, and said is was a casting defect. Four more sections went out over the next two years. Labor costs are killing me, and the manufacturer said no more - it must be a problem on my end.

Any speculation on what could be the root cause of our corrosion problem? [Our house is a two-pipe steam system, low pressure, no condensate pump.]

As far as I know, we did not alter any of the variables in our home's heating system or in the basement boiler room. I originally thought our old boiler died of "old age", but based on all of the corrosion problems on our new system, it is possible that there has been some variable in our total system that has changed and is leading to the corrosion problem.

We live in Wichita, Kansas (pop. 400,000). The water supply used to be groundwater from our fabulous aquifer, but depletion has led to using supplemental water from a nearby reservoir in the city water system. I believe this transition has been gradual over the last 25 years, so I think it is unlikely that a water chemistry change caused the problem.

Our old home shows signs of many repairs over the years. To my eye, some of the repairs appear to have been performed by "experts" and some appear to be clunky "homeowner" repairs. (I observe at least one repair to a bathroom radiator that looks to be homeowner clunky.)

Is there a chance that the wrong kind of pipe was installed during a clunky repair and created a galvanic problem due to incompatible metals being in contact? The original galvanized water piping in the house was replaced with copper in the 70s. Has house settling caused a copper water pipe to sit on a hot steam pipe and cause a galvanic reaction?

Is there a chance a leak has developed in the condensate return piping? If I had a pinhole leak in a vertical section, I don't think it would be revealed by a water puddle, yet could it continuously pull oxygen into the system? If fresh (oxygenated) air from the house is corrosive, could I have a faulty air vent that has failed in the open position?

In addition to proper care for my boiler, I am also worried about proper care for my steam supply and condensate return piping. If any of these lines go bad, it will be a very expensive repair because the steam system was obviously installed as the house was being built.

I did not see a sticky post on boiler maintenance basics. Can someone refer me to some of the better past posts on maintenance in case my search skills are rusty (pardon the pun).

On the other hand, if someone would like to make comments here concerning maintenance for my specific system it would be appreciated. I could use help on proper maintenance (or best practices) during the running season, and for the spring shut down.

Thanks,
Rod

Fred

How much fresh water is being added to the boiler? How frequently? Leaks in the wet returns won't draw air in that will do damage. The system is open to air whenever is is idle.
Do you store any chemicals in the immediate boiler area? Some detergents, bleaches and other chemicals can be corrosive.
Are you sure it is corrosion? Is the near boiler piping correct? Are ther swing joints from the risers to the header? If the risers go directly into the header, without swing joints, the expansion and contraction could put stress on those end sections and eventually crack them, causing leaks. Something is certainly not right there.

KC_Jones

In addition to what Fred said post some pictures of the current boiler install so we can get a look at what you have going on.

MilanD

If it's galvanic corrosion you suspect, follow pipes and look. Usually, any reaction would appear downstream of the contact spot, but not in the boiler. I'd suppose you would see rust and failure on pipes closer to the contact spot. But again, I can't see how something like this would rust out the boiler so quickly.

What brand and model is it that failed? This may be an issue someone here had with the same model.

From my limited knowledge, sounds like your water is bad: either acidic for some reason, or very high on chlorides, or as @Fred said, plus perhaps a lot of makeup water being used. All of this would have a quite deteriorating effect on the boiler. There was someone here on the wall mentioning multiple boiler failures, 18 months between each. I think in their case chloride levels were through the roof.

Abracadabra

add a water meter and keep an eye on the readings.

MilanD

Sorry, it was 3 boilers in 18 years... So not quite after one year...

http://forum.heatinghelp.com/discussion/160219/third-steam-boiler-in-18-years#latest

ChrisJ

Keep makeup water to an absolute minimum.
Oh and use a good water treatment like Rectorseal Steamaster or a product from Rhomar.

MilanD

Is using Rectorseal Steamaster safe for older pipes?

BobC

My pipes are 96 years old and it does not bother them one bit.

Bob

ChrisJ

MilanD said:

Is using Rectorseal Steamaster safe for older pipes?

It reduces corrosion, so absolutely.
Also, none of it should end up in the steam piping as a properly piped boiler produces distilled water leaving the treatment behind.

Even my wet return is pure clear water with a TDS level of 1 to 2 PPM.

MilanD

Great! How often you add it? I read here 2 tablets tops on regular system. Our boiler is a tad under 2000 edr, LGB 7. Should I use one at a time until pinkish water in the glass? (Sorry, usurping the post, but perhaps this is beneficial to OP too).

BobC

One or two is fine for the typical residential steamer, but a boiler rated for 2000 EDR is going to contain a lot more water so I would start with two and be prepared to add more. You can use PH paper to check the results the next day.

Bob

ChrisJ

BobC said:

One or two is fine for the typical residential steamer, but a boiler rated for 2000 EDR is going to contain a lot more water so I would start with two and be prepared to add more. You can use PH paper to check the results the next day.

Bob

Bob,
No need to check PH.
Steamaster seems to be around 9 or 10 it self, meaning no matter what you do, it won't exceed that.

After adding Steamaster, blue water means the PH is too low. Purple means the water's PH is safe. Off the top of my head, I believe purple was 7 or higher.

Fishin_Rod

Fred,

No chemicals or cleaning fluids stored in the boiler room. I am not aware of any changes we made in the usage of the boiler room from the time when the boiler ran fine to the onset of extended boiler problems.

The header was changed (a little?) when the new boiler was installed, but I believe it has swing joints (opinion of non-expert homeowner).

The current boiler uses very little water. It does not have an automatic filler. I manually add water when I flush the low water cutoff valve. I normally do this approximately once/week during heating season. However, when I forget for a 3-week gap, the boiler water level is still right at normal.

Abnormal water loss is what initially alerted me to a problem with our replacement boiler. I started adding water daily just to keep the cutoff switch happy. I finally took the hood cover (?) off to inspect the boiler sections during operation. At operating temperature, steam was blasting out of a large hole. The surrounding cast iron was so rotted that it flaked off like brown sand if just brushed with a screwdriver.

I termed that "corrosion", but commentators should consider that my descriptions are from a "homeowner" vocabulary and not an "expert" vocabulary with exact and proper usage.

P.S. I will post pictures when my daughter with the good camera comes home.

Thanks,
Rod

Fishin_Rod

Milan,

I am not knowledgeable enough to suspect galvanic corrosion. I was just brainstorming based on the maze work of utilities that run through my old house.

The replacement boiler is a Dunkirk Model 400 Base.

Fishin_Rod

Abracadabra,

Since I don't have a water meter, do you think I should just mark my exact water level on the sight glass when the boiler is cold and see how many weeks I can run until I reach the low water cut-off? (Or slightly before that point for safety reasons?)

There is a plug in a tap on top of the boiler that is the twin of the tap where the pigtail is connected. Could I just use a funnel at that tap and measure the gallons of water it take to hand-fill my system back to the original water level?

Fishin_Rod

Chris,

The installer said "clean" water would turn to steam much more efficiently, and I "couldn't get the water too clean".

Consequently, since I have had multiple sections replaced in the "new" boiler, I frequently drain some water through the low water cut off valve while the boiler is operating. (He said that was the best time, because the sediment was stirred up.)

At the start of the season, I probably do this 3-10 times/week because the drained water is very dirty. I try to minimize the makeup water, so I only add a little water after every 4-5 squirts.

I add the water during a boil cycle, so it should de-oxygenate immediately. I also keep my hand on the copper water pipe and only fill with 70 degree water that was "in the house". Once I hit cold (40 degree?) water from outside, I close the valve before it reaches the boiler.

Feel free to comment on this practice and the stupidity thereof. If this is not stupid, then please comment on ways to improve my water cleaning.

I also drain some water from the bottom of the boiler, from the bottom of the loop, and from the bottom of the lowest condensate return line at least once during the winter.

At this point in the season, when I squirt the valve at the base of the low water cutoff, I see a plume of dirty water rise up in the sight glass. However, during normal boiler operation the water in the sight glass is very clean.

What is the proper trade-off between draining "dirty" water out of the system versus avoiding the need to add makeup water?

Fishin_Rod

Chris,

I am a petroleum geologist. When they were replacing my second set of boiler sections, I mentioned to the installers that we have some oil wells that also suffer severe corrosion problems. We use a class of chemicals called "corrosion inhibitors" in these wells. In certain circumstances they are amazingly cost-effective.

I asked if they had any similar chemicals for use in boilers since repeated steam cycles seemed to have a lot of corrosion potential to me. He said that there was no such product - because it would just boil away.

That sounds like exactly the type of product you are describing with the Rectorseal or Rhomar chemical. Is there a good existing thread on these products that someone can link, because Milan also appears to have questions? Should I start on new thread on that topic?

MilanD

If what you are saying is true, only thing I can think is water quality. Check your city water report to start, for chloride levels. Most municipalities have this report available online. This may have changed recently unbeknownst to the public. Then, test your makeup water. Chloirides do not have ppm requirements per EPA regulation but high concentration can wreak havoc on the boiler. Each time makeup water is added, it stays in the boiler and concentration of it is elevated further.

Fishin_Rod

Milan,

I am not a boiler guy, so I am just speculating off of your comments.

I assume a steam system loses a little water vapor to the atmosphere through the main vent, the air vents at the radiators, and through any leaks in the system. Since this is distilled water (or water vapor) that is lost, then the water that remains in the boiler will always continuously increase in chlorides!

Should I fill my boiler with distilled water at the start of the season? Is there some "rule of thumb" for how often you should completely drain your boiler and start over with clean water - even though the entire boiler contents would then be fully oxygenated? Is that better than running water with high chlorides?

Inquiring minds want to know. Are there any experts on "best practices" that can chime in on this topic?

Rod

MilanD

Rod,

I too am a user of steam bolier at work, so what I've done and learned is a process through which I am still learning. That said, I am trying to give you ideas as far as my knowledge goes, plus some thinking based on what I've read and learned so far here and elsewhere. Naturally, professionals here will have greater knowledge.

Yes, some water evaporates. No, you don't want to change out all the water often. That has its own set of issues, namely - oxygen in water. You want as dead of water as you can get, and slightly alcaline. Can you use distilled water? Yes. But read on.

Corrosion of boiler castings has to come from an unfavorable combination of O2, H2O, air, and other chemicals and processes, the combination of which will eat a thick piece of iron quickly. Black iron pipes themselves and alone, can last 100 years or more. Heck, there are some 80 year old boilers still working today. Now, pipes develop a layer of rust that protects the inside of pipe from corosion. Old boilers, on the other hand, were cast very thick so it takes 80 years for them to go. Some pipes are prone to develop pinhole leaks, usually where there is pooling of water, a sagging, or at a joining of pipe and a coupler, or another fitting. This is where the pipe is thinnest due to threads being cut in. But this too can take 50-80 years. Old cast iron fittings (els, tees, etc) were well and thickly cast back in the day and they will usually rust at the end of the thread and pipe joint, under certain circumstance. I removed one 1922-installed ellbow recently, solid is ever. But, they also only carry water and steam. There is no fire burning them hour after hour... No solids, as you said, only distilled steam and water with atmospheric air going in and out of vents.

Back to boiler: yes, solids and chlorides increase in concentration with each fill. Then, there is a process in the boiler, well documented in high chloride levels, by which there will be some kind of chemical reaction which will turn cast iron into, essentially, a block of graphite. Pros can chime in on that in more detail. Something to do with how tds and chlorides attach themselves to the inside wall of the boiler and create a hotter spot on the casting. As I underatand it, fire passes on the opposite side, and heats this small buildup on the opposite side and inside of the boiler, to the temperatures exceeding the normal temperaturea seen on the non-tds laden iron. Now, hotter than normal temp creates chemical reaction eating away at the iron. There may be some small electrical current created by the flame too which speeds up the proccess. I may be off on this exact proccess, but some kind of reaction eats the iron and essentially burns throug the boiler. And quickly.

Yes, there is a way to treat the water, and that was mentioned previously with 2 products. Second one, Rhomar, I believe will ship you buckets of the fluid to use instead of water. Here, again, I'd bow to the pros on recommendation. I'm not sure which is better and if Steamaster will reduce chlorides as well as all the TDS, or if you can start with 25 gallons of distilled water. But here too, first test the city water you have.

Second thought: 400 model is close to 1000 EDR (the sticker calls it sq.ft of steam). That's a lot of radiators. Has the replacement boiler been sized correctly?

If you are oversized, and have borderline water quality issues, you may be doing a lot more firing, as it's called "cycling on pressure". This means more fire in the casting than for a properly sized boiler and again, speeding of the deterioration, as above.

Also, from my novice look through the manual for this boiler, piping per manufacturer instructions look quite different from what pros here do. Does your install job near boiler piling look like the manual? If so, you are good. Improper piping can also haste the deterioration. This can create wet steam conditions that would carry chlorides and dts up with the steam, again quickening the demise.

Then, is your water gauge showing nice and even bobbing of water when steam is created, or is it more violent and, perhaps also foamy? This too needs to be correct. You may need skimming.

Finally, the chimney. Is it drafting sufficiently? There could be a mosture issues under the draft hood which will eat the top of the boiler. There was a thread here recently, of someone who had to reline the chimney after boiler rusting through. Again, this too is possible. Pros can talk more about this.

In the end, if you have boiler failure and will need replacement, make sure someone does the EDR calculation for propper sizing of the boiler, and whatever is installed, that the piping is done at the minimum per installation manual, or better, with a dropped header. Then, continue with skimming and checkout, and finally that there is a propper water quality, and that the chimney is working properly.

Trick will be finding someone who really knows steam to do all this. In the process, depending on where you are, the knowledge just might have to come from you to get to the bottom of this.

Best of luck!

Abracadabra

Fishin_Rod said:

Abracadabra,

Since I don't have a water meter, do you think I should just mark my exact water level on the sight glass when the boiler is cold and see how many weeks I can run until I reach the low water cut-off? (Or slightly before that point for safety reasons?)

There is a plug in a tap on top of the boiler that is the twin of the tap where the pigtail is connected. Could I just use a funnel at that tap and measure the gallons of water it take to hand-fill my system back to the original water level?

I find a water meter to be the easiest and most accurate way. I'm sure that there are other ways. Either way, you need to track your water usage.

Fred

@Fishin_Rod Said: When they were replacing my second set of boiler sections, I mentioned to the installers that we have some oil wells that also suffer severe corrosion problems.
@Fishin_Rod , This statement says a lot and may well be the first clue to your problem. Do you know or can you find out what caused this corrosion? If you can get a copy of that report, that may show something important. I have to believe it is probably water borne, maybe something in the soil that leaches into the water. Maybe a combination of chemicals/minerals/whatever. What is the source of water for your town/city or are you on a well? What you describe certainly is corrosion. Personally, I don't believe chlorides alone will do that much damage (four sections in a two year time frame) but who knows. Also, to have a 92 year old boiler die of severe corrosion (while that may have been pure and simple age) it may also be an indication of the time frame that something significantly changed, give or take a two year window in time. Did you city change its source for water? Is that the time frame when they began drilling those oil wells? If you are on a well, was a new well drilled around that time? Something changed. At a minimum, you should have your water tested and see what story that tells.
As it relates to your boiler practice, draining some water 3 to 10 times a wekk is not good. If the boiler water is dirty (which it likely will be with all that corrosion), drain the boiler at the start of the season and refill the boiler with fresh water and bring it to a boil. Then do your blowdown weekly. I assume you have a float type LWCO, like a McDonnell Miller #67, since you are doing te weekly blowdowns. Probe type LWCO's don't require that blowdown. Also, until you solve the corrosion problem, I would refill the boiler with each blowdown and not wait to do several blowdowns before adding water. If there is something in corrosive the water, you may well be concentrating that, in the boiler with each blowdown where the water is not replenished.
I believe @Larry is a chemist (if my memory serves me correctly) Maybe he can weigh in on this.

Larry_52

Federal law (clean water act) requires your water company to provide an annual water report. Find this and post it.

Distilled water in a home boiler to me is overkill, but if your source water is that bad it might be worth the effort.

At a minimum you should listen to Chris and start testing your boiler pH now. A test kit for TDS and chlorides and results posted from boiler would help too. I would recommend rector seal steam master tablets, I use them out of ease of treatment and maintenance.

The dissolved O2 issue is always there as when the boiler is at rest for prolonged periods the top of the water level becomes saturated with O2 again. You could add sodium sulfite to a residual of 50ppm to scavenge, but are you going to buy a test kit and monitor it on the off season? The steammaster tablets will assist in developing a protective layer that can inhibit O2 pitting so again better than me recommending a demin w/ caustic and sulfite dose to maintain.

Thanks @Fred for the vote of confidence, although I did take boiler chemistry in college, I am not a chemist.

ChrisJ

Fishin_Rod said:

Chris,

I am a petroleum geologist. When they were replacing my second set of boiler sections, I mentioned to the installers that we have some oil wells that also suffer severe corrosion problems. We use a class of chemicals called "corrosion inhibitors" in these wells. In certain circumstances they are amazingly cost-effective.

I asked if they had any similar chemicals for use in boilers since repeated steam cycles seemed to have a lot of corrosion potential to me. He said that there was no such product - because it would just boil away.

That sounds like exactly the type of product you are describing with the Rectorseal or Rhomar chemical. Is there a good existing thread on these products that someone can link, because Milan also appears to have questions? Should I start on new thread on that topic?

Hi Rod,

I just drained my boiler last night due to a leaking drain valve. After this, I refilled, skimmed a gallon or so out for good measure and tossed in two Rectorseal Steamaster tablets.

Water treatment doesn't "boil away" because you're producing distilled water "steam". The treatment stays in the boiler.

Notice the purple water in my gauge glass, that's from the water treatment.






I'm not sure if there's any Steamaster available on Amazon anymore, but you can get a good product from Rhomar as well. Not only that, but Rhomar sells something they call "boiler fluid" that is premixed water, ready to add.


http://www.rhomarwater.com/products/catalog/boiler-pro-903

Boiler Pro 903 is a fantastic product. Steam-pro is their "boiler fluid" but don't use this if you're going to add water manually from your water supply.

If I was you, I'd try to buy Rectorseal Steamaster tablets. If you can't find them, buy a jug of Boiler Pro 903 from Rhomar. The Rhomar stuff is likely better, but a bit pricey.

hot_rod

First knowing the quality of the fill water is critical to the longevity performance, and efficiency of any boiler, steam or hydronic.

Two inexpensive meters will give you a very good idea of what you have in your water.

IF the water does not meet the specification listed in the manufacturers manual, technically you have no warranty or recourse.

Until recently boiler manufacturers have been accommodating, know that the fluid quality is the main cause of failures.

Times are changing, manufacturers of all hydronic and steam equipment are rethinking the warranty procedure. Chloride levels especially are increasing in our water supplies.

Realistically it is not that hard to identify "bad" water or fluid with a TDS meter. And also not that hard to condition tap water if it is out of spec.

More and more wholesalers are making the equipment, or the pre-filtered water available understanding the cost and hassle involved with failed equipment that is fluid related.

Here is an example of water requirements that I show in training from several boiler manufacturers.

Indirect tanks also has water quality specs listed.

Softening water will remove some of the scaling components from the water, but not all the harmful ions. In fact softened water can actually increase the TDS, via the ion exchange with the brine, and increase electrolysis corrosion potential. You have put in a stronger electrolyte!

New England SteamWorks

Oops, accidental bump...