Closing Test Cocks on the Double Check.

Posted on: January 10th, 2012 by NickMillward Posted in Uncategorized

Test Cock

So you’ve turned on your sprinkler system yourself in the spring and have gotten squirted in the face by one to four full force jets. You jump up from the valve box furious at your incompetent sprinkler guy who obviously didn’t winterize correctly. Now you’re positive your backflow preventer has a freeze break.

Well, let’s check the test cocks first. Take a look at this photo (click on to enlarge). The flathead screwdriver is inserted into the slot of a test cock. There are four test cocks on every double check valve assembly, (only 3 are visible here). When a system is winterized, the water is shut off and blown out with a compressor or drained. The test cocks should all be opened to drain the backflow and left open all winter. They should be turned at a 45 degree angle, as well as the handles. Ball valves trap water in tiny spaces at the top of the valve when fully open or closed. This small amount of trapped water will expand and crack the brass.

Another good reason they are left open is if the main shut off valve for whatever reason is defective in a way that makes it slowly leak, the sprinkler mainline will eventually refill with water and freeze. If the test cocks are open, at least the water will spill out right away before entering the mainline. Some shut-off valve leaks (weeping) are so slow they aren’t detected at time of winterization.

Note: the backflow preventer and double check terms I use refer to the same device- the brass thingy with two (usually blue plastic coated) handles. Backflow preventer is the generic term, and double check is the specific type of  device. You’ll hear the two terms used interchangably. There should be a separate shutoff valve upstream of the backflow that tees off your house water. Sometimes the backflow itself is the only shutoff. If this is the case, the first test cock cannot be opened to drain because it is upstream of the first ball valve. ( blue handle thingy )

Anyway- where were we? Oh yeah, let’s close the test cocks. With the water off stick a flathead screwdriver in that slot in the middle of the test cock. Sometimes the backflow is installed in such a position these are hard to get to. You may need a small mirror, flashlight, and/ or a stubby screwdriver.  Turn in any direction (it will spin around both ways) until the slot is perpendicular to the test cock itself (which will be parallel to the big backflow device). Make sure all four are closed. Now turn on the water. If you’re still getting a small squirt out of the cock (no giggling please) give another slight twist with the screwdriver in either direction until it shuts off completely. If you can’t get it to stop dripping there is something wrong and the test cock should be replaced. Call your sprinkler guy!