Sherlock Holmes has always been one of my favorite fictional characters. I envied how he would notice each detail and use every one of his senses to solve the crime. I live by the adage, “Always assume there is a problem in the boiler room.” I try to pretend I am like the famous sleuth when in-side a boiler room, trying to uncover the hidden problem(s). 

Before starting, I ask the onsite person about issues they are having with heating the building. Assuming there is a problem, I often ask, “What areas of the building are the hardest to heat?” As you know, once you visit a new job site, you tend to inherit all the problems in the building. Knowing this, I make a note of the problem areas mentioned in the service report to protect my company.

When walking into a boiler room, I like to open the exit doors. My personal CO detector is clipped to my belt to alert me if there is elevated carbon monoxide present in the room. Once the room is considered safe, I close the outside door to simulate the actual operating conditions. Another habit of mine is to memorize the boiler room exits in case something happens. If a boiler room fills with steam, the oxygen is displaced resulting in difficult breathing and visibility drops to zero, essentially blinding you. 

Glancing around the boiler room, I scan for clues on how the boiler is operating. The first thing I check is for excess rust below the draft diverter of the water heater. If there is a mound of rust, it tells me the flue gases are not properly vented. Misdirected flue gases can cause the formation of carbon monoxide. 

Another indication of improper flue venting is black streaks around the burner entrance to the boiler or on the sides of the water heater or boiler. A discolored boiler jacket can also indicate improper venting through the boiler. The causes of these conditions are typically insufficient combustion air, blocked flue passages, low water temperature or a negative condition in the boiler room. 

It only takes -0.03” water column to pull the flue gases from an atmospheric burner. If excess rust or black streaks are evident, my first step is to verify the combustion air openings are clear and adequately sized. If the openings are correctly sized and unobstructed, my next task is to investigate the source of the negative condition. 

It could be an exhaust fan in the boiler room, or something in the building. Once I eliminate the boiler room, I move on to the building. To do this, I open the boiler room door to the building a half-inch or so and test if the air is moving from the boiler room into the building.


A simple way to check is to hold a small strip of toilet paper or tissue in the opening. If the tissue is pulled away from the boiler room, I know something in the building is not right. One building had an inoperative makeup air fan and the building exhaust fans sucked the flue gases from the water heater and boiler. 

Leaking pipes are one of the fastest ways to kill a boiler. The leaking pipes will allow fresh untreated water into the system, which will increase water treatment costs and introduce scale and oxygen into the system. I like to document any leaks and inform the owner. 

Scanning the boiler room, I look for items stored there which may not be compatible with a flame. The boiler room seems to be the warehouse for anything the owner wants to keep out of sight. One school had chairs surrounding the boilers, making it almost impossible to access the boilers or escape if needed. Weil McLain has a whole list of things to avoid inside a boiler room. These include:

  • Spray cans containing chloro/fluorocarbons;
  • Permanent wave solutions;
  • Chlorinated waxes/ cleaners;
  • Chorine-based swimming pool chemicals;
  • Calcium Chloride for thawing;
  • Sodium Chloride for water softening;
  • Refrigerant leaks;
  • Paint or varnish removers;
  • Hydrochloric or muriatic acid;
  • Cements and glues;
  • Antistatic fabric softeners used in clothes dryers;
  • Chlorine type bleaches, detergents and cleaning solvents found in laundry rooms; and
  • Adhesives used to fasten building products and other similar products.

I would wager you have seen one or more of these items on your last boiler service call. 

Eyes open

A dripping boiler relief valve could indicate a flooded expansion tank, defective relief valve or excessive system pressure. 

The PTA or pressure-temperature altitude gauge on the boiler can help troubleshoot the heating system. It takes one pound of pressure to raise water 2.3 feet. If the highest radiator is 100 feet high, divide the height of the highest radiator by 2.3 and add three more pounds, and that is the pressure the gauge should read. 

(100 / 2.3 = 43 psi 43 psi + 3 = 46 psi)

This formula only works if the boiler is located in the basement of the building. If the boiler is in the penthouse, I like to set the system water pressure for 10 to 12 psi. 

If the owner told me the top floor of the building has trouble heating, I would verify the pressure is correct on the PTA gauge. The PTA gauge can even tell you if the expansion tank is flooded. Watch the PTA gauge as the boiler fires, and if the boiler pressure on the gauge rises steadily as the boiler fires, this usually means the expansion tank is flooded.Incomplete combustion will leave a tell-tale odor that burns your nose. If I smell this acrid odor, I shut off the boilers and water heater and open the outside door to the boiler room to ventilate it before determining the source of the smell. 

Listening is also an excellent way to uncover hidden problems inside the boiler room. Squeaking may indicate a defective blower, induced draft motor or pump. A failing blower motor may sound like pieces of sandpaper rubbing when the motor is stopping.

If you hear what sounds like the snap, crackle, pop of the cereal Rice Krispies when the boiler is firing, this could indicate scale formation on the waterside of the boiler. Scale can lower the efficiency of the boiler as well as drastically reduce the life of the boiler. Next time you are in a boiler room, remember, “The game is afoot.” Have fun, detective.