A hot tub is a wonderful thing to have. If you have built your own, you will need to plumb it. Once the jets, heater, blower and pump are in place you will need to connect them. Flexible PVC pipe is the best to use around the hot tub to connect the jets. However, when you are connecting the heater, blower and pump you are going to want to use the rigid plastic pipe. Measure all around your tub, first, then measure the distances from your blower and pump to the jets. These measurements will be the length of PVC pipe you will need. Also, you will need to use glue that is specially designed to "weld" PVC, this is available at the hardware store where you purchase the pipe. Be aware that PVC pipe cannot be unglued once it is glued, your best bet is to test fit everything before you glue.
Assemble all of your pipe, connectors, and glue before beginning.
Choose flexible PVC pipe that matches the connectors on your jets, this can be either 1 or 1 1/2 inches in diameter. The jets require water and air, that is why each jet has four connections. The top are for air and the bottom are for water.
Run the flexible pipe close to the tub connecting each jet, top and bottom. Avoid sharp right angle turns.
Connect an air regulator to the top of the tub to allow air to come in.
Seal off the ends of the water and air lines, closing the system.
Connect a length of flexible pipe to the air passages under the tub and then to the blower.
Connect your hot tub it in the following order, to make it run properly. Skimmer - Pump - Heater - Filter.
Connect the drain to the skimmer rigid pipe of the appropriate size. Rigid PVC pipe is important here because of the pressures required to make the pump work correctly. Flexible pipe allows for pressure loss.
Use rigid PVC pipes in either 1 or 1 1/2 inch sizes depending upon your pumps. The flexible pipes do not hold up to the pressures required to run the pumps. Try to avoid 90º angles.
Install one cut-off valve before the pump, one after the pump, and one on either side of the filter so that you can isolate the pump and filter when you clean the tub or in case of an emergency. Also install a drain faucet before the filter, because it aids in draining your tub when cleaning.
Make sure everything is correct, then glue it. When the glue is dry, fill the tub with water and turn it on. Reglue any leaking connections.