If your well casing is 3-4" we recomend using a 3" Grundfos Pump. 4" Pumps will fit into 4" well casings but 15-20 years later pump may not be able to be removed even with a rig and you will be forced to drill a new well so it is a worthy investment to put a 3 Pump instead. We also carry other Grundfos Pumps We also carry a variety of sizes of Fiberglass Pump/Pressure Tanks. About Us: We are a family owned Heating and Plumbing business.We have been in business for over 50 years. We have a customer base from word of mouth referrals(not mass advertising). We rely on repeat customers. So you don't have to deal with various people that can't find your order. The item "Grundfos 3 Submersible Well Pump 15SQE07 180 3/4HP" is in sale since Monday, May 16, 2011. This item is in the category "Home & Garden\Home Improvement\Plumbing & Fixtures\Pumps". The seller is "hhpac" and is located in Alliance, Ohio. This item can be shipped worldwide.