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How to Fill an Antifreeze Sprinkler System

Darby Stevenson

Wet sprinkler systems feature pipes that are always filled with water. These systems can douse a fire faster than dry systems, whose pipes fill with water only when you activate the sprinklers. Since sprinklers occasionally pass outdoors or through unheated parts of a building, however, there can be a danger of the water in a wet system freezing. For this reason, antifreeze loops are often installed on the areas of a freezer system that are prone to freezing. You can fill the antifreeze loop through the antifreeze fill cup.

Replace the old antifreeze in your antifreeze loop to keep the sprinklers functioning properly.

Step 1

Find out how much liquid you need to fill the antifreeze loop of your sprinkler system. You may be able to learn this from the building's maintenance supervisor, the original sprinkler system design blueprints or the manufacturer of the sprinkler system.

Step 2

Mix with water the amount of antifreeze you need to make its freezing point below the coldest possible temperature in your area. Ask the supplier of your antifreeze what this exact amount is. For example, if the coldest temperature experienced in your area is -22 degrees F, you will need to mix 60 percent glycerin antifreeze with 40 percent water, or 50 percent propylene glycol antifreeze with 50 percent water.

Step 3

Locate the fill cup and drain valve for the antifreeze loop. This will be near the entrance to the unheated or outdoor area of your sprinkler system. Near the fill cup will be a large plastic expansion chamber connected to the main line, featuring twistable knobs on top and underneath. The backflow preventer, on the main water supply and surrounded by two control valves, will also be near the expansion chamber. The fill cup will be an open funnel facing upward; the drain valve will face downward. Both will feature twistable valves.

Step 4

Open the drain valve and drain the old antifreeze solution into large plastic containers that you can take to a disposal site.

Step 5

Close the drain valve. Open the valve near the fill cup.

Step 6

Pour the new antifreeze solution into the fill cup until the system is full. Close the valve near the fill cup.