Below is a thread that we modeled our home built mechanical releasers after. We have built two of these and have been pleased. For floats we used stainless steel containers that would be used in your kitchen for a cookie jar or sugar/ flour storage. We punched a hole in the top and bottom with a body punch, made a sleeve with pvc water pipe and threaded fittings on that with o- rings to seal it. $5 dollars for the container at Ollie's Bargain Outlet and a couple of bucks for fittings. As far as large diameter pipe for the releaser goes we used 10 inch inside diameter pvc water line supplied by a brother in law that is in the construction business. Very thick walled and easy to thread. Capped both ends with 1/2 inch plexi and an o- ring. If you know anyone in that business they may be a good source. I picked up another section of pipe recently when driving by a waterline project near home. I saw a 2 foot piece on the ground and asked about it and they were glad to get rid of it so they did not have to carry it to the dumpster. Haynes built a releaser setup with kegs so he may be able to answer your question regarding vac levels that they can withstand. If I had a choice of mechanical or electric I would certainly choose electric. These releaser work good and we are able to pull 26-27" of vac consistently but are not nearly as efficient as the electric releaser. Rather lengthy cycle times with small cfm pumps. On one we use a small 2.5 CFM A/C pump and the other is a Gast 1550. The 1550 cycles much quicker than the A/C pump.
http://mapletrader.com/community/sho...emade-Releaser