Bulkhead fittings are used in plumbing when you have an aquarium typically. Mainly they will be needed if you have a pipe that goes out of the aquarium through one of sides or the bottom. If you have never worked with one before, there really isn't much to it. Here are a few materials that you will need to finish the task and some steps to help guide you.
Step 1 - Familiarize Yourself
If you have never worked with a bulkhead fitting before you may want to familiarize yourself with the different parts of it. Basically the plumbing part attaches to the body of the bulkhead fitting, the nut holds the whole thing together and then there is a rubber seal that is around it to help keep the water from leaking out, making this a great fitting for an aquarium.
Step 2 - Determine the Size
To determine the size of the bulkhead fitting that you need, you will want to decide how much water will actually be flowing through it. Typically when you buy the bulkhead fittings you can see a chart with maximum flow rates listed on it for each size. You will be able to match it up to see the smallest that you can get without going over. You will also need to take the size of the hook up from the aquarium into account to make sure that it fits. This can typically be done by eying it or with a measuring tape. Many times you will need to use trial and error.
Step 3 - Clean the Parts
Now that you have picked the parts that you are going to use, you will want to clean them. Use a Q-tip to get around the smaller parts depending on the size of the fitting that you got and a cloth to get the rest of it clean. It is okay to just use water, but if you want to use soap, be sure you are using something that is aquarium safe as the water that will be running through will have fish in it and you don't want to harm them with chemicals.
Step 4 - Install Fitting
To install the fitting, put the bulkhead fitting through the hole on the aquarium. Then, put the rubber seal on so that it can protect the bulkhead fitting and keep water from coming out and tighten the nut up with your hand as much as you can and then use a wrench if you feel that it needs to be tightened any more. Be sure to go through and make sure that everything has been tightened up.
Step 5 - Test Out
Now that you have everything set up, you can plug the aquarium in and make sure that everything is working properly. You should be able to run it without any leaking or problems.