1. If you got the 750 cc double balloon rectal catheter as a retention aid and you have medical problems and are in a wheelchair, you probably bought the wrong double balloon rectal catheter. The 750 cc double balloon rectal catheter requires a "straight shot" of at least six inches from the tip of the nozzle to the end of the inner balloon inside your rectum to be cleaned out BEFORE you will be able to insert this. For many people, going that far brings you to the start (or end, depending on how you look at it) of the sigmoid colon. The 500 cc double balloon rectal catheter requires only about 4 1/2" to insert it, and that makes it much easier to insert so the inner and outer balloons will be in the right place. The 500 cc double balloon rectal catheter gets just about as wide as the 750 cc, but the 750 is oblong when inflated, not a round ball shape like the 500 cc.
Cleaning out the rectal area will obviously require a small enema before inserting the 750. Now, you must be sure ALL the enema solution is expelled BEFORE you try to insert the 750 cc balloon, because it isn't all clear, you will leak some remaining brown fluid when doing the insertion, and that will be very messy, especially if you do not have good mobility, and you probably don't want to have to call someone to clean up after you for this. I would also recommend doing your entire enema procedure in the bathroom, NOT in bed at all.
2. You do NOT need a three prong speader. Those are for other types of fun.
3. The silicone double balloon rectal catheter is durable, but you must take care of it and keep the valves dry at all times.
4. My husband and I have several double balloon rectal catheters, and when we use a 750, we use at least 6 pumps, often 8 pumps. The reason you need to almost fully inflate it is because if you don't, the fluted shape will actually direct the water you are trying to retain right out of you and onto the bed, floor, etc. The balloon must be inflated so the inner part is resting against the anal ring and the balloon is fully rounded out. The anus will not seal against the fluted shape of an incompletely filled balloon.
5. The fact is, you might do MUCH BETTER with a RUSCH double balloon rectal catheter because both balloons inflate with a single squeeze bulb, but more important, those balloons are completely ROUND. They are smaller balloons, and they will be easier to insert. The smaller balloons shouldn't be a problem in retaining the enema solution.
*******Probably the best thing for you would be to have a hand shower hose connected to your bath shower and use a connector to attach a regular colon tube in place of the hand shower spray. You will need a 1/2" threaded connector and a piece of 1/2" hose barb to attach the colon tube. Then irrigate your colon with it while sitting on the toilet, clenching your anus to retain the fluid and just relaxing it and removing the colon tube to release. Letting the water in and out several times should do a very good job clearing your colon.
I hope this helps.