Peggy says: Although the 4 gal salt tank WITH pump can be used with any toilet, IMO makes no sense to buy that one for use with a raw water toilet, because the pump is neither needed nor serves any useful function when used with a raw water toilets, it just cost a lot more...$288 list price for the 4 gal tank without pump vs $373 for the one with pump. Since both use rock salt--which is a great improvement over the 2 gal brine tank--there's nothing to be gained by spending the extra money. Bill says: There are a several of reasons to select the tank with pump. No. 1 Location. With the pump tank you have a lot more flexibility as to where you put it. The little pump is quite good and can easily pump the brine thru 10-15 feet of the 3/8" plastic hose that runs from the tank to the LS. As long as the tank is level with or no more than 1-2 feet below the LS it could be in the next compartment, in a hanging locker or in our case just inside the storage compartment under the lavatory. Easy to get at to add salt. With the NO PUMP tank it needs to be a reasonably close proximity, no more than 6 feet away, to the hose that runs from the seacock or on-board tank to the toilet pump and level with the toilet. No 2 Plumbing With NO pump you must cut the toilet intake hose and insert a valve body into it. Never a really easy thing the do with sanitary hose but a hair dryer or heat gun helps. Don't forget to double clamp because chances are this valve is below the waterline. The seacock is for sure so unless you put in an anti siphon loop with a solenoid valve to close the vent when the pump is running, this junction could just sink you if the hose slips off the valve you just inserted. With tank WITH pump drill a little hole in the top of the LS, glue in the barbed fitting Raritan furnishes and connect the soft flexible 3/8" hose from the tank to the LS. BOTH tanks require pressurized fresh water from the boats onboard system so the plumbing there is most likely a toss-up. No 3 Regulation of the amount of brine used. The NO pump tank has an adjustable pinch-clip similar to one you might see on an IV bag at the hospital. By trail and error you determine where to set this clamp so that the proper amount of brine mixes with the input water as it enters the toilet bowl. When the water temperature changes, not slightly but if considerably, the amount needed can change so in order to optimize salt usage you may need to adjust the clamp periodically. The WITH pump tank pumps brine straight into the LS when and only when the LS controller senses that it is required. Nothing to adjust. No 4 Electrical Tank WITHOUT pump requires none. Tank WITH pump requires that a small two conductor wire, furnished by Raritan, be run from the tank to the control board on the LS and a heat sink is clipped onto a transistor also on the control board. No 5 Drain It is recommended with BOTH units that an overflow hose be connected to the overflow fitting at the top of the tank. This is primarily for when filling with salt. If the tank is full of water/brine when you add more salt, it will overflow and Raritan has made accommodations to handle this by draining it into the bilge. I have not in three years connected a hose to the overflow. When we get ready to add salt, we turn off the water going into the tank, I put a ball valve in the pressurized water line just before the inlet, cycle the toilet a few times which causes the pump in the tank to send brine to the LS and lowers the level enough to add salt without overflowing. Conclusion (as seen by Bill) the tank WITH pump serves a few useful function. You don't have to cut into and form another potential leak in a thru hull hose. You don't have to worry about optimizing the brine input to the LS. You have greater flexibility in finding a convenient location for it. And if you are operating in fresh water only, you keep salt out of the toilet and its components. Lastly when we change to a fresh water flushing toilet, and we will someday in order to eliminate the noise, I don't want to have to change salt tanks. All of which add up to well worth the 30% difference in price IMHO. Bill PS: I greatly respect Peggy's opinions. When it comes to sanitation on the boat and the handling of poop, etc., we live by most of them but I just happen to disagree with her on this subject.