While working toward my DIY canister filter idea I have been experimenting with different materials and techniques. I thought I'd throw out some pictures of different things I've tried. I'd like to get comments on ways to improve what I'm doing or better ways to do the same thing.
I'm working with 4 inch schedule 40 pvc pipe and 3/16" pvc sheet. Right now the pipe I'm using is the basic cellular core stuff used for sewer pipes. The pipe is light and plenty strong, but cut surfaces are rough because the inside of the pipe wall is foam. I think to get a smooth cut I will have to get solid pvc pipe. Solid pvc pipe is used mostly for large water lines, so it's hard to come by in small quantities. I may have to buy 20 feet to get any at all. I'm trying to avoid using standard plumbing fixtures because I don't want the end result to look like a sewer line.
The first pictureshows an assembly that includes most of the details I've worked on. Two sections of pipe are joined together by two door hasps. The joint between the two pieces of pipe is a seal. A filter would be built similarly, but it would be 14" to 17" high and (obviously) it would be closed at both ends.
The second picture shows the two sections separated to show the seal. I cut a deep groove into one section using a 1/8" single-flute router bit and seated a 1/8" cross section Viton O-ring in the groove. The opposite side is cut to fit into the groove. When the hasps are latched down the top part seats against the O-ring. This seems to work in theory but has several problems in practice. First the Viton (aside from being expensive) is probably firmer than it should be. I might use a Buna-N or (if I can find it) silicone o-ring. Second, the cut surface is a little rough. A cut on solid pvc should be smoother, but I don't know if it would be smooth enough. That's why I think it needs a softer and more forgiving o-ring. Last, the door hasps work great, but they are very difficult to adjust. Once the last screw hole is drilled there is no way to loosen or tighten the joint. If the two hasps aren't evenly adjusted the seal doesn't work right. Does anyone know of a different kind of latch that might be used?
The third picture shows an alternative to the first seal. It is just a rabbet cut into each side so the pipe fits together. The seal would need a gasket. So far the only gasket I've tried squeezed out of the joint as soon as it was compressed. Any other ideas?
The fourth picture shows the end of the pipe. The end is made by cutting two disks from 3/16" pvc sheet -- one the same size as the inside of the pipe and one the size of the outside of the pipe -- then fusing the disks together with solvent cement. To make the disks I cut squares from the plastic sheet and drilled a 5/32" hole in the center of each square. The hole fit on a 5/32 inch steel post in a jig that let the piece rotate while I cut it on a router table. The jig was also used to hold both disks in place while they were fused together. The two fused disks made a single 3/8" thick disk with a rabbet around the edge that fit snuggly over the end of the pipe. The disk is fused to the end of the pipe with solvent cement. The hole in the middle of the disk can be plugged with a piece of 5/32" pvc stock The hole can also serve as a pilot for a large hole drilled for a fitting.
The piece shown is my only attempt so far. The seam between the pipe and the end leaks, but could be sealed from the inside.
The last picture shows a way I found to make pieces to thicken the inside of the pipe. This can be used where screws might go through the pipe wall or where I need something to support screens or internal baffles. I cut a 1.5" x 2.5" piece of the pvc strip like the one sitting in front of the pipe then put the plastic strip in a pot of boiling water so that it could heat and soften. Once it was hot I took it out of the boiling water and held it against the inside of the pipe (ouch! hot! hot!) When it was cool I had a plastic strip that fit exactly to the curve of the pipe.
I have still not decided whether I will a) build a submersible pump into a chamber inside the canister b) mount a power filter pump to the top of the canister or c) use an external non-submersible pump. I'm leaning toward a) because I think it might be quieter. Any suggestions?
I did try drilling and threading a hole in the side of the pipe for a 1/4" NPT fitting. It was fairly easy to do and held a brass fitting very well. I would not use brass in the actual filter. I also want to use 3/8" fittings or larger. With the larger hole I might need to thicken the wall to get a strong joint.
Comments and suggestions, please!
Roger Miller
I'm working with 4 inch schedule 40 pvc pipe and 3/16" pvc sheet. Right now the pipe I'm using is the basic cellular core stuff used for sewer pipes. The pipe is light and plenty strong, but cut surfaces are rough because the inside of the pipe wall is foam. I think to get a smooth cut I will have to get solid pvc pipe. Solid pvc pipe is used mostly for large water lines, so it's hard to come by in small quantities. I may have to buy 20 feet to get any at all. I'm trying to avoid using standard plumbing fixtures because I don't want the end result to look like a sewer line.
The first pictureshows an assembly that includes most of the details I've worked on. Two sections of pipe are joined together by two door hasps. The joint between the two pieces of pipe is a seal. A filter would be built similarly, but it would be 14" to 17" high and (obviously) it would be closed at both ends.
The second picture shows the two sections separated to show the seal. I cut a deep groove into one section using a 1/8" single-flute router bit and seated a 1/8" cross section Viton O-ring in the groove. The opposite side is cut to fit into the groove. When the hasps are latched down the top part seats against the O-ring. This seems to work in theory but has several problems in practice. First the Viton (aside from being expensive) is probably firmer than it should be. I might use a Buna-N or (if I can find it) silicone o-ring. Second, the cut surface is a little rough. A cut on solid pvc should be smoother, but I don't know if it would be smooth enough. That's why I think it needs a softer and more forgiving o-ring. Last, the door hasps work great, but they are very difficult to adjust. Once the last screw hole is drilled there is no way to loosen or tighten the joint. If the two hasps aren't evenly adjusted the seal doesn't work right. Does anyone know of a different kind of latch that might be used?
The third picture shows an alternative to the first seal. It is just a rabbet cut into each side so the pipe fits together. The seal would need a gasket. So far the only gasket I've tried squeezed out of the joint as soon as it was compressed. Any other ideas?
The fourth picture shows the end of the pipe. The end is made by cutting two disks from 3/16" pvc sheet -- one the same size as the inside of the pipe and one the size of the outside of the pipe -- then fusing the disks together with solvent cement. To make the disks I cut squares from the plastic sheet and drilled a 5/32" hole in the center of each square. The hole fit on a 5/32 inch steel post in a jig that let the piece rotate while I cut it on a router table. The jig was also used to hold both disks in place while they were fused together. The two fused disks made a single 3/8" thick disk with a rabbet around the edge that fit snuggly over the end of the pipe. The disk is fused to the end of the pipe with solvent cement. The hole in the middle of the disk can be plugged with a piece of 5/32" pvc stock The hole can also serve as a pilot for a large hole drilled for a fitting.
The piece shown is my only attempt so far. The seam between the pipe and the end leaks, but could be sealed from the inside.
The last picture shows a way I found to make pieces to thicken the inside of the pipe. This can be used where screws might go through the pipe wall or where I need something to support screens or internal baffles. I cut a 1.5" x 2.5" piece of the pvc strip like the one sitting in front of the pipe then put the plastic strip in a pot of boiling water so that it could heat and soften. Once it was hot I took it out of the boiling water and held it against the inside of the pipe (ouch! hot! hot!) When it was cool I had a plastic strip that fit exactly to the curve of the pipe.
I have still not decided whether I will a) build a submersible pump into a chamber inside the canister b) mount a power filter pump to the top of the canister or c) use an external non-submersible pump. I'm leaning toward a) because I think it might be quieter. Any suggestions?
I did try drilling and threading a hole in the side of the pipe for a 1/4" NPT fitting. It was fairly easy to do and held a brass fitting very well. I would not use brass in the actual filter. I also want to use 3/8" fittings or larger. With the larger hole I might need to thicken the wall to get a strong joint.
Comments and suggestions, please!
Roger Miller