Sealed Lead Acid Battery Problem?

I have a sealed lead acid battery of 7.5 Ah from my computer UPS. it shows diminished performance but charges to 13.2 volts. I think the liquid inside it has evaporated. I am thinking of converting it to a flooded lead acid battery and use it for my emergency lantern. can I convert the sealed lead acid battery to a flooded one by pouring battery acid in it? then i could maintain it by adding water from time to time. is there any risk? will the battery work?