Do you mean the strainer on your shurflo pump or submersible pump? if it's on your shurflo pump, just unscrew it when your tanks empty run it under a tap to un-clog and clean it then replace it. You can then prime the pump by running it on full flow for 10 minutes or so returning the water back into your tank. Works for us and we do this on each pump maybe three or four times a year.
Yes that's the one tosh at the minute I've taken off one like this picture below Just wanting to no if the shurflo type can go under water as I might buy two of them.