For additions to a home sprinkler system, can I add control valves downstream of an antisiphon valve? Some plumbing books and one RainBird sprinkler info sheet says to do this. Other internet sites say to avoid possible damage to the antisiphon valve, no other valves should be installed downstream of the antisiphon valve. My particular setup makes it difficult to add antisiphon valves to the existing manifold of 2 antisiphon valves.