I would NOT put anything that has SH running through it inside a box with a battery. That pump is Glass/Poly. It WILL eventually leak (pump chamber and pressure switch are the most common culprits) and when it does, that is what is known in the Roof Cleaning Industry as a BOMB. SH and Sulphuric acid do not like each other.
Don't believe me? Ask Chris Tucker at Apple about the time some roof cleaning fluid ran under the hood of an old pickup truck parked next to a customer's house.
Personally, I would mount it outside. Heat kills those pumps. This is why there are some companies selling auxiliary heat sinks for them. The only alternative is to mount it in a box with a big 12v fan with intake and exhaust ports.