Why ever buy a used boiler? For economic advantage, obviously. The motivations may vary widely, from a low budget fixer-upper owner project to a pro bono effort by a well-intended mechanic, but the risks and value results nonetheless remain the same.

Our comments are purposely being limited to Weil-McLain Residential (Gas & Oil) Water and Oil Steam Boilers, our specific area of expertise. Northern New England offers us particularly good insight into higher demand heating systems and their effects, with over fifty years of observed results. As people we all age differently and more or less graciously — similarly with boilers.

Extending this point, a boiler’s age or appearance is incidental to its performance. Recently pulled 50 to 100 (yes, 100) year old boilers still looked pretty good, yet you couldn’t afford to feed them.

The age varies but 15 to 20 years is a fair economic life of a boiler, considering heat exchanger and combustion design efficiency progression over this period. Personally, we won’t consider anything over five year old steam and ten year old hot water — and even then with an eagle eye. Furthermore we use trade costs in our consideration.

First and foremost, there is a great potential difference in life cycle between a hot water and a steam boiler. Specifically:

  1. A hot water boiler operates at a much lower average demand temperature (usually up to 180-190°F) with no state change (boiling) involved.
  2. A steam boiler must operate at boiling (212°F) and significantly higher to distribute heat as a vapor. The state change (boiling) accentuates chemical actions within the water and ultimately will deteriorate the boiler castings. “Steamers” therefore must be considered separately from “Hot Water” Boilers. They just live differently!

Similarly, so-called “Dry Base” Boilers must be disallowed under any conditions. Definition: A Dry Base Boiler is a design variant where the boiler sits over the combustion device (burner), as opposed to having combustion occurring within the boiler. (Picture it as a kettle sitting over the burner on your stove.) The easy way to tell is if the lowest (return) pipe enters the boiler above the burner level. Dry Base Boilers, particularly those fabricated from Steel Plate rather than Cast Iron have very limited life and are viewed within the heating community as “junk boilers” — sold on price alone.

The latter, more desirable and more common “Wet Base” Boiler has its lowest (return) pipe very near the bottom of the boiler and is intrinsically more efficient than the “Dry Base” Design. Combustion occurs completely within its heat exchanger castings. Getting down to the specifics in qualifying a used Weil-McLain Boiler (we are admittedly terribly opinionated), you must look beyond the seller’s story and get down to these facts:

  1. Determining the actual age of any Weil is relatively simple. Every Weil boiler has a “CP Number Label” affixed either on the front or left side of the enclosure. Weil Tech Service can tell you exactly when and what was made.
  2. A Gold Series Enclosure indicates a 1995 to Present build. A Blue (Presidential Series) with corresponding small label near top left front of enclosure indicates a 1985-1995 (approx.) build. Prior Blue or unlabeled boilers are just too old to consider.
  3. The new Weil-McLain Ultra Series Condensing Gas and Triple-Pass Oil Boilers are designer packaged with tan lower and black top control cabinetry. Introduced in 2005/2006 they are as pretty performing as they are appearing. Unlikely that these have hit the used market yet, but you never know.
  4. We don’t deal with the pre-2005 Gas Boilers and therefore exempt ourselves from their discussion. Frankly, the jump from 80-83% of these to the 93-98% AFUE’s of the Ultras just doesn’t make economic sense.

Once you’ve determined that your “find” is a candidate, grab a Heating Mechanic and go — the same as you would for a car. His expertise should determine exactly what you are getting in terms of wear and tear, parts replacement and condition. Generally speaking:

  1. First look closely for leaks originating between the boiler “sections”. (Cast boilers are similar to a loaf of bread, i.e. a “crust on both ends and slices in the middle”, tied together with rods.) Seam stains, rust trails and debris are indicative. Walk away! This is a catastrophic condition on all boilers.
  2. Specifically on Steam Boilers remove the covering and look at the top of the boiler. If it has a rusty red to orange color, then it has been “cooked” (overheated, likely due to low water malfunction). It may be still running, but likely not for too long since its life has been severely compromised. Don’t walk but run away!
  3. Look for leakage around the immersion heater bolts, flange and/or blank-off plate. This is from poor maintenance with possibly some deterioration of the casting resulting. Crusty rusting with wet tracking throughout bolting — watch out!
  4. Determine that any other staining, etc. is from piping and related devices that leaked and tracked onto the boiler and not from within itself. Boiler water condition is important, too. Internal black “goo” is a no-no.
  5. Has the unit been scavenged for controls, valving, its burner swapped or missing? Most Weils come with (our preferred) Beckett AFG Burners, but Carlins and Riellos are offered options. Leaving a poor burner behind is not the worst of options if replacing with a new/newer unit.
  6. Steamers with an electronic auto water feeder and low water cutoff are much preferred. If they stay behind or the unit has the older, cast, black McDonnell-Miller Low Water Cutoff, deduct significantly for it. They suffer immediately from poor maintenance.

Q. Where do we shop for used boilers? A. Large Cities that have Natural Gas Service.

There is a perpetual turnover of oil and natural gas conversions in the Northeast/Middle Atlantic Corridor. We use Greater Boston in our market but note that NYC/NJ is very active, supply and pricing-wise. There are smaller markets in Hartford, Providence and Albany but pricing is typically much higher. The rural areas are worst in our experience. Maine, Northern NH and Vermont are just out of touch with reality! Their asking prices are twice the Boston Area, and travel up to 400 miles to boot? No.

Watch the Internet for the best deals. (Ebay is not very active for the used market.) Craigslist is fine, but be quick and be smart! The rural “PennySavers” are useless. Word of mouth within the trade is very good also. A short time between availability and closing the sale is paramount. Be there first and negotiate with cash in hand!

Pricing? Just remember that the scrap value of $100/150 is the starting point. Anything above that is negotiable. You don’t care what they paid to have it installed; only what you can replace it for with an incentive to do so. Just how much risk can you afford? The top end would seem to be about $1000 for a very good, near new system — all considered in our area. Example: We recently purchased a very large 2007 Weil-McLain Gold Steamer with Carlin Burner and Controls, documented used only one season for $1000, 40% of Trade Cost, 40 miles away. Mint Condition. It has been upgraded to the AFG and Electronic Water Feed System for about 60% of Trade. Beautiful System!

We have just skimmed over this subject matter. A lot of detail is necessarily omitted.

Whether you are buying a horse or a boiler, bring the expert with you. Also figure how you are going to get it home! Also, a deal is not a deal unless it matches your application. Ultimately you have to feed the horse, or your boiler. Do your homework first.

Last Edit: 10/10/2012