This question came up today. I mentioned the author might be better served on the DIY site as its more of a plumbing question than anything else. Should we welcome general sprinkler system questions or should we push them towards DIY? I realize this would be directly related to the care and maintenance of a garden/landscape, but it is truly a plumbing question is it not?
This is definitely a plumbing question. In my opinion, it is related to gardening...but getting a response from gardeners in this realm gives you no unique insight that a plumber would not have. In fact, a DIY plumber would be much more qualified to help you than a gardener. I think that question should be closed as an off topic question.
The question fails my (unofficial) criterion at point #3. It's only tangentially related to gardening and could find answers at the DIY site.