Pool Leak from Liner, piping or what??

[pectin]

We moved in to an old place [23 yrs old] with a 16 x 32 [22,000 gal] pool. Somehow during the day the water dropped to 6 inches. I was thinking the pool had a leak but when I filled it up again today [with all 3 skimmers on - top, bottom and side jets] the water fell to only about 1 inch or so... where is the problem actually. Also behind the yard there were quite a lot of sand [obviously I think from the Pool [hayward] filter. I did not see the sand initially coming. I had an algae problem and backwashed a few time and also did a rinse for over 2 weeks. Pool is getting more clearer now to almost as before, I went under did the "dye" test and remained still but could not find the leak. I may have missed some but in the night I saw no bubbles etc coming up. I check all the skimmers, piping, etc but nothing amiss. What is happening? Is it a liner leak, piping, or when I was running the Barracuda G3 all day 24/7 for the past 7-8 days straight that caused the leak then?

[mr_clean]

The first thing you can do is fill pool to normal level and leave it off for 24 hours and see if you loose water. If you do, let it go down and see if it stops and levels off, but do not let it empty. where ever it stops you can inspect anything just above it. Skimmer, return-lines, pool-light ect. If it seems it wants to empty, then holes on bottom or bottom of walls, steps, etc.
If you do not loose water, then it's pipes or equipment. You can check backwash trap and see if pipe is leaking water when pump is running. If you have multiport valve the rubber spider gasket could be bad. If you have push & pull backwash unit the piston O-rings could be bad.
Is there any water loss around equipment? Is there muddy areas next to cement by possible garden? Knowing if it's in pool or only when pump is running is a good start and loosing water is going to cause algae problems as chemicals are lost also.
Baracuda should not cause water loss and good saftey if water ever gets below skimmer for some reason to save pump.