Weil McLain steam boiler and water treatment

Gotta love 8-way! I added enough to get my pH to 10-ish or so as part of my end of season maintenance, sometime last May.

I haven't touched my boiler since then and just drained a little out of my float-type LWCO and my boiler drain and the water came out crystal clear. That means zero corrosion!

In my strong opinion, anyone with a recent vintage boiler would be a fool not to keep the PH at 10-11 and minimize draining. In the olde days, the castings were insanely thick apparently, and a boiler could last 100 years with just regular water (see Cedric).

That's not the case today.

But I believe that with just minimal treatment and attention to the water, you too can have your boiler outlive you. In your case I would strongly consider not draining the entire boiler. Just drain enough until the water runs clear. Then add just a little 8-way (my favorite additive)— like 3 ounces. It will free up some gunk. Let it run for a couple weeks. If it surges (marked by a dramatic drop in the gauge glass during steaming), then drain and refill and again add a little 8-way. When the water is finally staying clean, it will hardly get dirty at all if you keep the PH at 11.

When you drain it yearly now, does the water start out brown and then go clear after a gallon or so?

Shameless plug for my video showing my year-long corrosion experiment

Wow, that is kind of alarming. If 8.5 is fine and 9.0 causes the destruction of their seals, that is a problem. Even though the PH scale is logarithmic, it's very difficult to try to hold a line between 8 and 9 PH. I have seen in the WM manual they do say 7-8.5

If your story is true, and I have no reason to disbelieve you, I would not recommend a WM boiler.

Did they deny your warranty claim based on 9 PH in your boiler?

Only added 18 gallons last year.

Only?? 18 gallons is kind of an outrageously high amount of water to use in a year!

a lot of steam manufacturers and professionals would disagree that 7.2 is good enough to inhibit corrosion.

Of course a lot of manufacturers and professionals erroneously think the equalizer affects the “A” dimension so I’m hardly one to rely on an appeal to authority argument.

Do you have any data to back that 7.2 value up? Not challenging, but honestly asking.

I don’t put a lot of weight behind Cedric—he was built when castings were far different than they are today I believe. He probably could have survived this long with vinegar in his veins. Out of curiosity, does Cedric have the elastomer gaskets that modern W-M boilers have between sections?

Info that I find says that in the range of 4 to 10, normal corrosion occurs, and a somewhat protective layer of normal iron oxide forms. I think we see this inside our old main pipes and return pipes. Below 4 the acid removes the protective layer leaving the iron exposed to faster corrosion. We see this when people use vinegar or other acids to remove rust.

But at 10+, a different oxide is formed that causes corrosion to dramatically reduce (I am not a chemist):

Some DOE nuclear power article about iron corrosion

This article also notes that de-aerated water at high temperatures (with chart shown at 580F), corrosion starts to swing back up above 12.5 PH. I don't know if this affects de-aerated water at 212F but this chart fits with the non-Weil-McLain manufacturers' recommended high-end of 11 PH.

Other articles I found generally put it like this (my emphasis):

Within the acid range (pH <4), the iron oxide film is continually dissolved. In cooling water, the potential for calcium carbonate precipitation increases with higher pH and alkalinity; thus the corrosion rate decreases slightly as pH is increased from 4 to 10. Above pH 10, iron becomes increasingly passive.

Edit: I think I found the article that is the source for a lot of these other references on the internet. It is related to corrosion via pitting in nuclear containment vessels.

Cedric is a plain vanilla Weil-McClain 5-80. Yes, it does have the elasomeric gaskets (which will last forever, unless they are installed incorrectly or subject to base attack).

And you are quite correct, so far as I know, about the iron oxide which forms with the pH between about 4 and about 10. Perhaps more to the point, it forms at 7 to 8.5 perfectly happily, which is why I suspect that WM doesn't push higher pH values. It's the same oxide that the pH 10 range folks are pushing, so I myself don't see the point. You're not hanging anything…

On the other hand, so long as you are able to adequately buffer the water so it stays in the 9 to 10 range, you aren't hurting anything, either.

No, sorry @ethicalpaul !

And you are quite correct in the difference between various oxides of iron. There are two fundamental differences: Ferrous (Iron plus 2 valence) and Ferric (Iron plus 3 valence), and oxide (0xygen minus valence) and hydroxide (Oxygen/hydrogen covalent bond, minus 1 valence). They can be mixed, either physically or in a chemical mixture. The solubility of the various possible combinations (there are at least 12) varies with pH, but they are all soluble to at least some degree in acid (pH less than 4) water. None of them are particularly soluble in neutral to basic (pH greater than 7). Upon reacting with oxygen, the oxide forms — and it expands. Some of the oxides, however, form relatively good bonds with the underlying iron (or steel) while others tend to flake off. Fortunately, most of them do form decent bonds.

Of note and real importance is that once Iron is oxidized, either to ferrous or ferric iron, the presence of carbonic acid, sulphuric acid, or chlorides yields soluble free iron ions, and the rust instead of more or less staying put simply washes away. The presence of the two acids is minimized or eliminated by keeping the pH neutral or above provided the water has at least a minimal amount of Calcium (both the Cabonic acid radical and the Sulphate radical combine with the Calcium to form an insoluble material at neutral and above pH) with the presence of chlorides can be reduced only by ensuring that they are NOT present in the water (note that this is why the use of salt softened water is so lethal to boilers).

I've never treated or tested the boiler water since I bought the place 4 years ago. When I drained the water, just before turning it on for this season, it turned clear after about 4 or 5oz. (maybe less). The water in the sight glass is clear. I'm assuming i don't need to touch it.

It kills me that the previous owner drained and refilled the thing monthly. Can't imagine how many years of life he took from it.

I hope so. Thanks

8 Way is a very good buffer. Unfortunately the stable range is pH 10 to pH 10.5, which is fine if that is where you want it.

However. Since it is a very good buffer, you will need to get almost all of it out of there to get the pH to move much out of that range.

Up to you. Some here say that the boiler should be kept in that range, and the manufacturers are clueless. Some here say that anything more basic than 7 is fine. Some say you should follow the manufacturer's opinions.

Some of us just run tap water and have for years with not problem at all…

Probably shouldn't have said "unfortunately". However, the point is this: the buffer range of the 8 way seems to be from 10 to 10.5. What that means, however, is that the concentration of 8 way — the amount present in the water or initially put in — can vary over an extremely wide range, but the pH will stay in that narrow range. This is why buffers are so handy! But also why they are pesky — once there is any significant concentration of a buffer system in the water, that's the pH range you are going to have. If it's what you want, you are delighted. If it's not what you want, you are left with no choice but to get rid of the buffer system and start over…

I completely emptied the boiler and refilled it with fresh water. The ph is now about 9.7.