I don't install strainers for RPZ's
Can you Explain?
As TeaMan points out, the liturature I've seen for Watts regarding their 009 RPZ has the following:
We recommend a strainer be installed ahead of 009 series assemblies to protect
the internal components from unnecessary fouling.
Caution: Do not install with strainer when backflow preventer is used on seldom-
used water lines which are called upon only during emergencies, such as
fire sprinkler lines.