Plumbing checkvalve question

[JohnInSoCal]

Should there normally be a checkvalve after the pump but before the DE filter ? I am switching from cartridge to DE filter and my system does not currently have a checkvalve between the pump and filter but I was wondering about possibly getting DE back into the pool/spa when cleaning the pump basket etc. Maybe just a ball valve would be good ?
I do have a checkvalve after the heater because I have an inline chlorinator.

thanks,
-- john

[tphaggerty]

I have a check valve after the filter but before the solar (to prevent solar drain back through the filter). No check valve between pump and filter here.