It's time to plumb the tank!
Reef tank plumbing can be as simple or as advanced as the hobbyist wishes to make it. For the purposes of this document, simple designs will be discussed.
What are the parts that need to be plumbed?
Sump - The sump is merely a resevior that holds the overflow water from the tank. It should be kept filled enough that the return pump doesn't pull air, but empty enough that if the power goes out your tank won't empty into your sump or worse - your floor.
Return pump - The return pump's function is to put water back into the disply tank. The diameter of the pump's pipe should be less than the total of the drain pipes.
This pump is often used to create current in the display tank, and it is recomended that it have the ability to turn over the volume of the entire tank at least once per hour. In addition to providing return water and current to the display tank, return pumps can also be used to run protein skimmers, in-line chillers, and/or refugiums if they are sufficiently powered.
Return drain - This is a simple bulkhead placed inside the hole in the overflow. It should lead to the sump, and be neither too long nor have too many elbows which would restrict flow.
What plumbing components are commonly used and how are they used?
Bulkhead adapters - Commonly called tank adapters or just bulkheads, these expensive plumbing parts mate a flat tank wall into a pipe. They come in two flavors, threaded or solvent welded necks. The end outside the tank is threaded. Typically, slip necks will do for reef tank needs because a pipe is rarely placed in this end except when used in an overflow.
Unions - One of the most important parts for reef plumbing. It isn't neccessary to use these when initally plumbing the tank; however, if you intend to make the plumbing maintainable it is required.
Valves - Ball valves are the most commonly used valve to stop or throttle water flow. Ball valves are best used in an on/off mannger. The other common valve is the gate valve which is best used to throttle flow in a more precise manner than a ball valve could.
Union valves - This expensive plumbing component combines a ball valve with two unions on either end in a small package.
Can you provide a plumbing example?
With any plumbing application on a reef tank, maintainability needs to be kept into consideration. Simply put, nearly all of the plumbing should be able to be dismantled and reassembled without any loss of material.
A bulkhead will be fastned to the sump. A union and a ball valve should be plumbed close to the bulkhead, so that flow can be stopped prior to making any detachments. The ball valve should be as close as possible to the thing you want to isolate like the sump or pump. From the other side of the union/ball valve combo a pipe or hose should be connected to the pump's intake. Even better would be to have a second union/ball valve combo connected, once again as close as possible, to the pump's intake so that the pump can easily be removed from the system for maintenance.
Unions and ball valves allow for easy isolation and removal of plumbing sections
From the pump's output, use at least one union to between the pump and the pipe or hose leading to the display tank. A ball valve somewhere between the display and the pump's output might be desired if you wish to throttle flow. Never throttle flow at the input, and never throttle more than 50 percent.
What other general guidelines can you provide?
Keep the number of elbows in the system to a minimum. Too many elbows, especially at the input or output of pumps creates a lot of turbulance and friction which reduces the power of the pump.
Draw out your plumbing design in detail before you go to the store to buy the parts.
Do not assume that bulkheads have a standard drilling diameter. Bulkheads are produced by different manufacturers, and thus have different outside diameters.
Buy more plumbing components than you need. I wasted a lot of time driving back and forth to Home Depot for the odd piece here and there.
Use teflon plumber's tape for all threaded plumbing connections.
Test all bulkhead seals before you put them into operation.
Where can I purchase plumbing parts without spending a lot of money?
In general, most elbows, tee's, ball valves, and PVC pipes can be purchased at any hardware store like Home Depot. For the specialized pieces like bulkheads, unions, and especially union ball valves, lower prices can be found by shopping on-line.
I've purchased parts from Savko. They have low prices and a user friendly website.