Anti-siphon valve questions
When I moved into my house, all of the irrigation valves were seized up and the lawn was already dead (it was bank-owned before I bought it).
I decided to replace all the valves (this is after two years of dead lawn... heh) and I noticed that even though they are anti-siphon valves, they are not above all the sprinlker valves - there are areas of my yard that are higher than the valves. So clearly whoever did this originally didn't really understand what they were doing.
So my options now are to either
1) Have anti-siphon valves that are a few feet above the ground
2) Isolate the areas that are higher than the valves and instead run an underground line to those areas and install an in-place anti-siphon valve 6" above that zone - is this allowed/possible? I guess the underground line before the AVB might defeat the purpose but I'm not sure.
3) Install some other backflow prevention device - from what I've read about CA regulation, this would have to be a RPZ assembly which is expensive and requires professional install.
So if option #1 is to be it, how should I go about hiding the valves? Are there enclosures that are designed for sprinkler valves which are several feet (probably 3') high? Or do I have to build something out of retaining wall blocks or cement board or something?
Another thing I read in the course of my research is that the inlet pipe to the sprinkler valve needs to be metal until it gets 18" underground. Is this a concern? It is not this way currently. I have 8 zones so it's going to be a lot of work. It seems like this would also mean that the manifold must be metal, which doesn't make a whole lot of sense. I included the source link for this, if anyone can clarify that would be great!
Here is a link that might be useful: Source for metal inlet pipe requirement