Re: Low buck projects- Let's see 'em!
Any pressure washer pump with 3gpm output ,with ceramic plungers makes a good watermaker pump. The 540 GPD membranes fit perfectly in a 2 1/2 inch sch 40 pipe, for a membrane housing.
Composing heads costing hundreds of dollars can be home made for under $50. Sheet blocks can be made for under $2 ,which are far stronger than commercially made ones costing over $30. Just cut the cheeks out of 3/16th aluminium, round them off and put spacers, SS bolts and sheaves in. Sheaves can be cut out of 1/2 inch poly cutting boards with a hole saw, and the groove filed in with a round rasp.
Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"