Sand for Sand Filter how much $$$

I think I need sand for my sand filter it holds 300 lbs, first is 300 lbs overkill for a 27000 gallon pool and second how much does sand run a bag?

The reason I think I need sand is this, I went to purchase a knew pressure valve and it doesn't work, I took it off while the pool was running and the water whichj usually shoots about 10 or more feet in the air was barely even getting out of the filter, and this was after backwashing for 3 minutes and rinseing for about a minute. Any suggestions what my problem could be???

Filter size seems OK to me. But, what is a 'pressure valve'? You don't mean a gauge do you? Little more explanation is needed. If you do mean 'gauge' then flow is blocked somewhere before the filter because removing the gauge should indeed shoot out quite a stream. Adding more sand won't solve the problem.
Al

Gauge is correct term sorry. SO back to drawing board for me.

Well yesterday in the am my pressure gauge wouldn't read, and I thought it was dirty sand. So I come on here ask a few questions in a posts knowing that the smart peeps here could help. And guess what? They haven't let me down yet. I was told it doesn't sound like a sand issue sounds like something before the filter. SO I take apart my pac-fab challenger and the whole time cursing the pool gods, knowing the sand was the cause (shows you what I know) I see some pine needles wrapped around my impeller and just a bit gunked up so, laughing and knowing this was not the cause, I just took my fingers and went to work taking out all the gunk, and then put the pump back together. I then crossed my fingers and turned the pump on and dang if it didn't work like new. So who knew, well I guess the kind people here did, and I am gonna double post this. Just because the website has some excellent people and the original post is what helped me, so thank you all, that have helped me and the many others here that need the help.

BBB convert for life!!!

Always glad to hear about a happy ending with a cheap and simple solution.
Al