Just put in a 2 speed pump. On high my DE gauge reads 29 on low it reads 8. I have a 2# check valve in a 2" line going to the pool; on low it sits there and clicks and makes rushing sound (not loud, just noisier than the pump). Can I assume the check valve isn't really restricting flow? The reason pressure is 29 on high is I installed slotted return eyes and it raised that pressure by 5psi. Don't really care since I plan on running on low 8 hrs/day. Just curious what an expected filter pressure should be at low speed with clean filter.