After it's clean and dry, I spray the same stuff I put in my pool to stop algie.

At first thinking that this one light spray something to put out fire and flyby, but to my disappointment it went into the second tower.

Or is there something I can spray inside the cracks / breather holes in the brick that would stop the water from getting in. 

Burnt tupperware containers with a white powdery residue and empty spray paint cans. 

You can do same with garden hose and nozzle set on mist spray It is not a dangerous or hard job if you do it correctly.Here all you have to do is haul to the landfill yourself which is about 40 miles,,,a nice drive. 

Sometimes cats spray walls.

Milind,Yes, your solution will work and is the right way to do the repair, just make sure you seal all the threads real good and test the joints with spray to make sure no gas is leaking out of them. you may want to test as many of the old joints that you can as well, just to make sure no gas is leaking out of them.

What we did though was new tile on the wall, sprayed the tub white, did LVP flooring and installed a white shaker style double vanity.

Get a gun, get a taser, get pepper spray.

(I actually witnessed cats spraying in places I wouldn't have believed without seeing!)