Flushing and Draining Techniques

Once a year, the entire hot water and steam system should be flushed to keep the pipes clear and the water flowing freely. To flush the system, open the blow-off valve and let the water run off into a bucket until it runs clear. If the water still looks rusty after the system has been flushed, call a professional service person.

What You'll Need
You'll want to have these tools on hand to flush and drain the system:
  • Wrench
  • Garden hose

Hot water systems should be drained to prevent the pipes from freezing during a prolonged cold weather power failure. It may also be necessary to drain the system to make repairs. Here's how to drain the pipes:

Step 1: Turn off power to boiler, and let water cool until it's just warm.

Step 2: Turn off water supply valve, and attach length of garden hose to boiler drain.

Step 3: Open drain valve and air vents of all radiators. Water from system will flow out through hose. Give valve plenty of time to drain.

Step 4: To refill system, close air vents on all radiators, and shut drain valve. Turn on water supply to boiler. If boiler has automatic shutoff, refilling is automatic. If there is no automatic shutoff, fill it until combination valve gauge reads 20 pounds of pressure per square inch (psi).

System Care Guide
There are myriad problems that can cause your system to malfunction. Click here for a troubleshooting guide for hot water systems, and click here for one on steam systems.

Step 5: Release air from all convectors in system so they'll heat properly. Gauge on boiler should read 12 psi.

If pressure on gauge shows less than 12 psi, add more water. If pressure is above 12 psi, drain off some water.

If you follow the steps in this article, you can be assured that your hot water and steam system will operate efficiently for years to come.

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