Without pre-filter quickly broken

We bought this sand filter system for our Intex pool. Actually, the sand filter pump worked well, but after a few months we had to complain about the sand filter pump, as they "gave up the ghost" Simply. The complaint was really governs quickly and easily by Bestway, we received a new sand filter pump sent. But even this was after a few months in operation broken again.

Meanwhile, we have the assumption that our two sand filter pumps are broke because simply lack the pre-filter in the system. We suck min. 1 times the week the floor of the pool, this so the entire protection has moved directly into the sand filter pump without pre-filter, perhaps that was the reason that both systems did not have a long shelf life.

Meanwhile, we have switched to a system with pre-filter and have no more problems.