What is a Calorifier?

A calorifier is a hot water cylinder. It stores hot water at 60 degrees C or hotter to kill Legionella bacteria. Over time, dirt and sediment build up at the bottom where bacteria can grow.

What to Check

Temperature

• Water leaving the top: 60 degrees C or hotter
• Water returning: 50 degrees C or hotter (55 in hospitals)

Outside

• Check for leaks, rust, and damage
• Check the insulation is intact
• Check the temperature gauge works
• Check the drain valve works

Inside (if you can get in)

• Look for scale build-up
• Look for sediment (dirt) at the bottom
• Look for rust
• Check the anode (a part that stops rust) if fitted

How to Do a Blowdown

Blowdown means opening a valve at the bottom to flush out the dirt.

1. Find the drain/blowdown valve at the bottom of the cylinder.
2. Attach a hose and route it to a safe place. The water will be very hot (over 60 degrees C).
3. Make sure the discharge point can handle hot water.
4. Open the valve fully.
5. Let the water run until it comes out clear (usually 30-60 seconds).
6. Close the valve.
7. Check the temperature goes back to 60 degrees C or hotter.
8. Check for leaks after closing.
9. Write down what you did.

How Often

• Blowdown: Once a year (or as the risk assessment says)
• Inside check: Once a year if you can access it
• Temperature check: Every month

Common Problems

• Temperature below 60 degrees C: Check the thermostat, the boiler/heater, and the circulation pump.
• Scale build-up: Think about descaling or water treatment.
• Lots of dirt: Do blowdown more often.
• Rusted anode: Replace it.