both in and out pipes are located at the top of the filter, the in pipe is actually above the barrel and plumbed to the bottom inside the filter. either tee'ed or your inlet hose ending just inside a larger down pipe. this way it will break the syphon effect before it happens, if you use A TEE you and hard pipe, instead of the upper elbo, (per SKIPPY'S instructions) you can cap the empty end sticking up,drill, and insert a small diameter tube, to create a 'venturi' adding oxygen to the water. the out pipe is located a few inches from the top.