@talhawaleed
Thanks for such nice comments from your side. I have kept this battery in very careful way and always maintain it with proper way.
Before flushing the battery, my battery was fully charged, then flushing is performed with acid of gravity of 1250 and battery is kept place for at least 30min before connected to ups.
After 30min of addition of new acid then battery is connected to ups with no load means when wapda is available. Then again battery was fully charged as well after addition of new acid.
Also acid level is fine not overfill-because I always take care the level of acid. So this is not problem.
You are right that some acid would come out if there is some overfill condition. 3 days has passed and no acid is coming out means spilled out acid was due to little overfill condition.
The backup time before flushing was 3.5hrs with load -one 21inch tv, 2-3 energy savours, one ptcl modem, laptop charging. After flushing, backup time is not noted due to no long outages except 1hr outages after very 3hrs..