DIY Air Pump Mufflers

 

I recently set up a 55 gallon tank in my office, and have all the filters and air pumps in the laundry room next to my office connected through a hole in the wall. I figured that I would finally not be bothered with air pump noise! Boy was I wrong.  It was still rather loud, and the noise was coming from the tank itself. Don’t believe me? I disconnected the lines from the pump, and I could not hear the pump in the next room, but when re-connected, NOISEY! Ever notice that your air pump gets quieter when you connect air hose to it? That’s because all that noise is going through the air hose into your tank. I wonder what the fish think of this? Remembering a diagram of how a car muffler works, I decided to build a muffler for my air pump.

The car muffler to the left is my inspiration. What I want is a chamber for the noise to expand and bounce around in before getting to my tank. Since I have many 9 ounce plastic water bottles at home, I will modify them. Besides, I want something small to fit under the tank easily or on a shelf. An online search of aquatic sites turns up other examples using glass jars, one and two liter plastic soda bottles, and even a tiny pill bottle. It is suggested that the volume of the muffler bottle will determine how well it works, but even a pill bottle will help. I decide to try and improve the design by adding filter floss inside the bottle, emulating the fiberglass packing that was in the car mufflers of my youth. I also build a single chamber and dual chamber muffler to compare the efficacy of larger volume and an hourglass shape.

 

First I drill a 15/64 inch hole in the bottom and top of the bottle. It is easier to drill the bottom with the cap screwed on the top, since the trapped air keeps the plastic bottle from collapsing as you press on it. Next insert the air hose through the holes. Unscrew the cap, put some filter floss in the bottle, and put the cap back on. Use some silicone sealant to seal around where the hose enters and leaves the bottle, let dry, and you are done! The upper right picture shows the final product.

Dual Chamber Muffler

 

The dual chamber muffler is only slightly harder to build. Two bottles will be connected together using a hole in the bottom of one and the threads on the top of another. I have noticed that the dual chamber muffler is somewhat quieter than the single chamber, either because of the larger volume or because of the hourglass shape of the 2 chambers.

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First use a one inch spade bit to drill a hole in the bottom of a plastic bottle. The one inch hole will make it possible to screw in the top of another bottle to connect them. Then use the 15/64 drill bit to make a hole in the bottom of another bottle, and a hole in the screw on plastic cap. Lightly fill the bottles with filter floss, then screw a bottle into the one inch hole of the other. Put on the plastic cap. You should have two bottles connected, with an air hose hole in the cap on one end and an air hose hole in the bottom of a bottle on the other end. Insert the air hoses, and use silicone sealant to seal where the hoses enter the muffler, and around the one inch hole where one bottle screws into the other. Let dry. You are done! The upper left picture shows the final product. Connect one end to the pump, use a connector to join the other end to the air hose going into your tank.

 

I think you will find that the pressure in the air hose goes down, the air flow out the airstones goes down a bit, and the noise entering your tank goes down A LOT! If you need high pressures or airstone flow, you might need a bigger pump after installing  a muffler. Try it out! Feel free to experiment with different sizes and shapes of bottles, use whatever  you have around the house, or whatever works best for you.

Long Term Follow-up

After about 8 months, the white caps on the bottles cracked or separated between the cap’s top and side. I would have thought the silicone joint between the tubing and the cap would have been the weak spot. Go figure. I had read that silicone bonds poorly to plastic bottle caps, but apparently not! No need to use a model airplane fuel line connector to go through the bottle cap if the silicone is stonger than the cap.