01/05/2023
Following the recent hard-freeze we are seeing several failures due to improper installation of Backflow Preventer Assemblies, specifically cracking of the lower ball valve.
In nearly every cracked ball valve we have replaced in the recent weeks there was no drain valve installed on the inlet side, although not a requirement, it is a best practice to ensure proper freeze protection in the event of a hard freeze.
Without an inlet drain valve the assembly cannot be adequately drained below the lower test-cock, which leaves water between the lower test-cock and ball valve. Additionally, we have encountered several installations which failed to include both an inlet (supply) shut off and inlet drain.
In order to properly drain an assembly to prevent freezing, several important points must be considered
1. The assembly can not be adequately drained through the testcocks alone.
2. Drain valves must be added on the inlet side and outlet side of the assembly below the assembly.
3. Compressed air of adequate volume may be used to “blowout” the system after the backflow preventer is drained.
4. After removing water from the system and assembly, the assembly shut-off valves, drain valves and testcocks should remain in a half open / half closed (45° degree) position to allow for full drainage of the ball valve shut-offs. The main shut-off to the system must remain closed during the winter period.
Proper draining procedure:
To drain the backflow prevention assembly for protection against freezing, use the following procedures:
1. Turn off the main shut-off valve (A) which provides water to the system.
2. Open all inlet and outlet drain valves on the system (B and E). Open inlet and outlet shut-off valves on backflow prevention assembly (C and D) and all testcocks. Leave in half open / half closed (45° degree) position to allow for full drainage of ball valve shut-offs.
3. Should you “blowout” the piping system downstream of the backflow prevention assembly, make sure the outlet drain valve (E) is open and the backflow prevention outlet shut-off valve (D) is closed.
4. Connect an air line to the outlet drain valve (E) and introduce air of adequate volume to clear downstream system of water.
5. IMPORTANT: After draining procedures on the backflow prevention assembly have been completed, all ball valves must be left in a half open / half closed (45° degree) position as shown in Figure A. Open the ball valve approximately 45° degrees while draining the pipeline and assembly to allow water between the ball and valve body to drain as shown in Figure B. Leave the ball valve in this position for the winter to prevent freeze damage
IMPORTANT: When finished, make sure main shut-off valve (A) remains closed to prevent accidental refilling of the system. AIso, the main shutoff valve should be resilient seated to prevent seepage of water into the system.
