"Hydronic Heating System - How to Empty a System"

 By Ron Stultz

8 November 2010

Background:

If you are lucky, you will never have to empty your hydronic heating system of water. In my case, home renovations caused baseboard radiators to be replaced or piping to be moved and thus my system had to be empty of water to allow for modifications twice

How to empty a hydronic heating system:

1. Close the shut-off valve on the water supply to your system. Not going to work trying to drain water out if the inlet pressure valve is putting water into your system.

2. Remove power from your system. Do this either at furnace switch or at circuit breaker box.

3. Let system cool, if hot. Cold water a lot easier to deal with that hot water, so drain your system when it is full of cold water.

4. Open all zone control valves manually. Do this by pushing the lever forward. There should be significant resistance as you push but lever will eventually stay in place, open.

5. Attach a garden hose to the drain faucet at the bottom of the circulator pump.

6. Now slowly open the faucet directly below the circulator pump. Water from you system should now begin to drain.

7. As the system is closed, eventually, water will begin to only come out of the faucet in gulps. When this happens, take a bucket and place underneath one of the zone loop drain faucets and slowly open the faucet. Some water could come out of this faucet but mostly you are opening a zone loop such that water can continue to flow towards the furnace and out the hose.

8. Once gulping begins again, open another zone loop faucet to open another zone loop to outside air and again, water should flow out the hose.

9. Continue to open drain loop faucets and let system water drain.

10. Water in the expansion tank, may or may not drain back down and out the attached hose. To make sure the expansion tank is empty of water, place a bucket under the faucet on the tank and open it. Some or a lot of water may come out.

11. With all zone loop faucets open, the last of the water in your system should slowly drain out.

12. Note that not every drop of water in your system is going to drain out. So if pipes have to be cut and soldered, best to make pipe cut and let water drain at cut until pipe is completely dry inside. Pipes that have any amount of water in them do not like to be soldered.