If you have more than one Waterwall Fatboy, you will need a Waterwall Joiner Kit for every tank except one - ie: 3 x Fatboys require 2 x Joiner Kits. Detailed instructions are included with the Joiner Kit.
Install and join each tank in sequence.
Before positioning the Fatboy tanks, drill out the lower outlets required in each tank for the connection hoses using a 1” paddle bit.
If your tanks are not positioned right next to each other, replace the hose in the joiner with longer hose. Position the tanks, screw the gate valve into one of the tanks; screw the hose section into the other. Connect the hose to the gate valve [with the swivel connection end of the hose].
Screw the air vented bung into the bung hole in the top of the linked tanks [not required in the tank with the inlet strainer]. Not venting linked tanks will void the warranty.
If you are in an area that experiences heavy downpours, you may want to link the tanks at the top as well as at the bottom - you can do this via the overflow positions using standard flange fittings and a section of straight pipe. This will ensure water rushing into the inlet tank can flow through to the linked tanks before overflowing.
If linking tanks on different levels overflow higher tanks into lower tanks. DO NOT link via the bottom connections as the additional pressure may damage the lower tanks and void the warranty.