Hmm, it looks like the one who installed the sump pump to your colleague at the mini, using his incompetence in the field. In general, the price of 1800 dollars is extremely exaggerated and inappropriate for such works. The price for installing a sump pump in a small residential home is about $ 250-300. In general, for more information, check out https://www.sumppumpadvisor.com/best-sump-pump-check-valve/
.I'm sure you'll find the answer to your question and even more information about this field. In this way, you won't commit the same fault as your coworker.