I just moved into a house with an ag pool, Hayward sand filter and Columbia PMX pump. I took off the cover on the strainer basket and water started flowing out such that I was unable to get the cover back on until the flow was slowed somewhat when my friend put a hand over the (I think) skimmer. I was only able to get the cover on partialloy as the O-ring got squished and now there is a continual low flow out of the strainer. There don't appear to be shutoff valves in the suction and discharge lines. How do I stop the flow so I can properly close the strainer lid? Thanks.