Question
You answered a similar question but I would like some clarification. Background: My sprinkler system was installed about 15 years ago and has worked reasonably well until recently when the pump housing failed with a large crack. I noticed that the outlet pipe (PVC) had pushed upward apparently putting enough stress on the pump housing to crack it. I ended up replacing the pump and now I notice that the same thing is happening. This pump is cast iron as opposed to the previous one which was made of some kind of fibrousness material. I don't expect the pump housing to fail as the previous did but the pipe could explode out of the pump, I suppose. The replacement pump is the same size (1 1/2 hp) as the previous one though its from a different manufacturer. The intake on the pump is 3" but I have a 2 1/2 inch feeder pipe going in. The output from the pump and the piping are 2 1/2 in. All piping is PVC, and all circuits (5) are working. The longest distance from the pump is about 200 ft., The number of heads per circuit is 5 to 6. What do you suggest for fixing this problem?

Answer
Thanks for your question.
The pump casing is certainly strong enough to withstand the stress of the plumbing connections. As for the pipe, it won't explode with the pressure from the pump. But, The stress at the threads where it connects to the pump might give-way.
Though not an easy fix, I would suggest replumbing the pipe and fittings to the pump. Be sure to secure the pump to whatever mounting pad you have. Just the vibration from the pump could affect the threads.

Matt