The Pressure Is On: Pumps in a Boiler System

The Pressure Is On: Pumps in a Boiler System

Your boiler makes steam. That steam is under pressure. That’s just how boilers operate. But as that steam is created, it lowers the amount of water in the boiler. That means feedwater has to be added. Otherwise, two things will happen. First, you’ll eventually run out of steam, literally. The second thing that will happen without feedwater is a low water level. You don’t want that, because it creates heat stress on the tank and promotes scaling and corrosion.

But we’ve already established that a boiler is under pressure. If you just open a water valve, that water isn’t just going to pour into the boiler as the boiler feed water is typically in an atmospheric feed tank or a DA that has 5-10 psi on it. The steam pressure will more than likely push the water back up the way it came, introducing steam into parts of the boiler system that aren’t designed to handle it. That means water has to be added under pressure, and that’s why boiler systems have pumps.


Pumps are responsible for introducing feedwater into the boiler under sufficient pressure that the steam can’t escape, so the boiler doesn’t lose the pressure that keeps it operating. The size and capacity of the pump on a boiler system depends on the operating pressure of the boiler, and the amount of feedwater that needs to be delivered over time. Obviously, larger boilers will have bigger pumps, and some even have multiple pumps to get the job done.


Boiler pumps are electrically operated. However, the amount of current that a pump will draw doesn’t necessarily correlate to the pressure it puts out. Pumps that deliver water under higher pressure will do so at a lower volume. That’s because pressure and volume are always inversely related; raising one lowers the other, and vice versa. Another way to think about it is in terms of a garden hose. If you put your finger over the end of the hose, you can make the water come out at a higher pressure the tighter you squeeze your finger over it. But the greater the pressure, the less water actually comes out every second.


As an interesting aside, the largest steam-powered water pump in the world, which is powered by the world’s largest steam engine (with a piston diameter of more than 12 feet), is located in the Netherlands. Found in the Dutch village of Cruquius, the pump was constructed in 1850 to help drain the 45,000-acre Haarlem’s Lake to reclaim land for farming. The pump house was eventually converted into a museum, the Museum de Cruquius, and is still open today with the massive steam powered pump as its main attraction. If you’re a real steamhead, it’s definitely on your bucket (valve) list.

If you need a pump, WARE’s online BoilerWAREhouse store carries a full range of pumps for every boiler size. WARE also has highly experienced technicians to install, inspect, maintain, and repair your boiler, as well. Let us know how we can help you.

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