A couple weeks ago I noticed what appeared to be a leak from the bottom of our 18 year old Hayward ST310T2 sand filter tank. There was water coming from under the base. I used a hole saw and put a 2" hole in the base and confirmed it was wet under the tank. I talked to my pool guy and he said they can crack at the seam so we ordered a new tank last week. Over the last few days the leak has seemed to dried up. Perhaps due to be doing a backwash and thereby reducing pressure in the tank? We noticed it dried up a couple days after the backwash. There has only been one day with a small bit of water since. I don't want to spend the $1500 in parts and labor to replace the tank if it is not cracked. I checked all other areas and fittings and found no leaks. Just confused as to how it has stopped after constantly being wet for a couple weeks other than less pressure in the system and it and the water is not being forced out of the crack.