I have a liquid fertilizer injection assembly before a set of rainbird drip irrigation valve assemblies. To prevent fertilizer from going back into the rest of the irrigation system, I added a PVC check valve just before the injection assembly (FYI: there is a separate RPZ backflow preventer at the beginning of the irrigation system).

The problem is that there is very little water coming out of the check valve. It is probably about than 1 GPM. The size of the PVC line and the inline PVC check valve is 1 inch. The pressure on the main line side of the check valve is about 90 PSI, so there is definitely enough pressure to open check valve. I cannot figure out what the problem is. The whole assembly is cemented very close to fit into a valve box, so I may have to cut and throw the whole injector assembly if I cannot find what the problem is.

My guess is that something got stuck in the inline check valve and it prevents water flow. Is there any way to verify/find what the problem is? I just added the PVC lines and the whole assembly and my first trial failed as described above.