Each water filtration system is built to ensure you have no drop in water pressure. We build the systems based on the amount of full bathrooms you have in your home. If you have 1-3 full bathrooms then selecting our 1-3 bathroom drop down will give you a flow rate of 9 GPM while our 4-6 bathroom unit will give you 12 GPM and 7+ giving you 17 GPM. Be sure when comparing our whole house water systems to others that you ensure that you have at the very least 9 GPM flow rate or you may experience drop in water pressure in your home.