Hello Udai.I saw your post on UBC a while back but I'm afraid I know little about this.
However here is a link that may be useful,if so you can do further research :)

Here is a link that might be useful: disease

The tree is suffering from humans. I don't know how long the pool has been in but that is what caused its poor condition. The tree is also poorly formed with two leaders. Though I can not tell from the picture, the oozing is likely to be slime flux. This tree will eventually die due to human damage. Have a certified arborist come and tell you if it is still safe. Enjoy it as long as it is safe, but plant a replacement now. Don't let anyone sell you cures for it like deep root fertilizer etc. you will be wasting your money.

Sorry for your problems but bet you a dollar water is getting in that pruning wound and rotting out the trunk.

Think about it festering in there then freezing and thawing this winter.

I have seen this on trees in my yard which i had to cut up. It is pretty neat to keep slicing pancakes from the trunk and watching the crack and rot through the trunk. I might even be able to postsome "inside" pics if I havent burned them yet....

If that tree was out in the middle of the yard i would say let it live till it falls apart but with where it is no doubt it will wanna splot and crack the pool.

Also, while tree "medical care" is still in its infancy notice if there was an accepted way to seal that pruning wound the water would have never gotten in there. What we do is akin to watching humans heal without bandaids

I agree with IpmMan. Most likely slime flux. Cause unknown, no known fix. Sometimes the tree grows out of it, sometimes it doesn't.

As was suggested should be evaluated -- by a Certified Arborist -- for potential hazard status.