I used to use a Magnum 350 as a vacuum cleaner for cleaning my tanks, I have a continuous water change system so I don't siphon crud out with the water changes, The Magnum worked ok but it plugged easily and didn't hold much plant matter. I have a lot of hairgrass that gets matted with ricca, java moss and bladderwort and is difficult to clean. The canister on the Magnum broke and a replacement was about the same cost of a whole new filter so a replacement was out of the question. I started thinking about what to use to replace my broken vacuum and after several failed ideas I came up with a small pool filter off of Craigslist for $5.00. After getting it home and looking it over, it had less space for crud than the magnum had.
I decided to use the pump, screw on lid and glue them into a larger canister for more volume, but come to find out the plastic they use can not glued.
I probably went overboard on this but I have fun building stuff.
I went back to one of my favorite materials to work with, PVC, I cut a length of 10" PVC pipe split and heat formed some flat material, I used another length for the body of the vac. I used a circle cutter on a router to cut round ends for the canister.
The pump slides up into the bottom and seals with an O-ring so I had to build up the thickness of the bottom for this to work. I cut a couple round plugs of PVC and epoxied them to the bottom with Super Glue Plastic Fusion.
To cut the round plugs and the precision hole for the pump to seal in I used an adjustable circle cutter in the drill press. it takes a few tries to get it set right but works well.
Here is the plugs glued on and the hole bored in it.
With the pump installed
On the inside I needed to mount the pool filter cartridge. I cut two disks of PVC to match the diameter of the cartridge and drilled the center of one for 1" PVC. I cut a length of 1" PVC and slotted it with a router bit in the drill press using a mill vise. Then glued that into the bottom disk and to the bottom.
I found one of my many test hole plugs that fit into the 1" tube, tapped it to 5/16-18 installed a stainless screw and glued it to the stand pipe.
With the filter installed.
after getting the bottom done I moved onto the top, I needed some kind of removable lid to access the filter and clean the crud out, I settled on a expanding 6" pipe plug.
I cut a short piece of 6" pipe and cut it into the top for the plug to work in, I don't have a pic of this stage but you can see it on the finished product and in the background of a couple of the previous pics.
Now the next part is the inlet to the canister, as a vacuum I want it to be smooth all the way in so it won't plug as the crud goes through. Any fittings would be a crunch point and cause plugging. I found a watertight electrical compression fitting that fit the tubing I was using for the intake, I also wanted the canister to swirl and keep the debris from blowing right into the filter. I drilled through the side with progressively larger drill bits and rotated each one to the angle I wanted the pipe going in until I ran out of larger bits I got up to 1" then I filed and fit until the 3/4" PVC pipe would go through. I glued the stub of pipe in with a female TA on the outside for the watertight fitting.
Ok that gets water in, now I have to get it back to the tank. The pool filter had a clamp on hose for the output so I had to adapt from that to a garden hose for the return. I found that the output size was close enough to 1" PVC that a compression coupling would clamp down on it.
I cut the compression coupling in half and a threaded coupling in half, glued the threaded coupling half in the compression coupling and installed a 3/4" NIP to hose adapter giving me a garden hose fitting on the output.
Glued the top and bottom in place, drilled a hole for the cord and output and installed the pump. used a couple more of the plugs from test drilling to tap and glue in the bottom, some 5/16 running thread and a scrap of aluminum bar to mount the pump and now I have a true wet vac.
Works great and holds more than I hope to ever need.
Future mods will include a handle to pick it up, it's kinda heavy when it's full, probably holds 3-4 gallons, and maybe a paint job.