Do tube diffusers have any advantages over circular diffusers?

With the same rate of cfm is a 2 head diffuser more effective that a single head diffuser and how do I quantify that?

Are Check valves necessary on diffuser bases or does it depend on the type of diffuser you use?

Carl

Circular or disk diffusers will have a slightly greater upwelling flow - maybe 10% more than tube diffusers. IMO tube diffusers are easier to clean and mount. Both styles have their benefits. I use both types in my pond. Multiple diffusers have more slits and bubbling surface area operating thus more water will be moved assuming a reasonable flow of air to each diffuser. with adequate air flow to each the volume of water moved is very close to the multiple of the number of diffusers. This has been tested and is represented on the Vertex website. Oversupplying air flow to a single diffuser results in the slits being forced open wider producing larger bubbles resulting in less water movement. The general rule in air lift technology is the smaller the bubbles and the more bubbles one makes the more water that is moved.

Many membrane diffusers have built-in checkvalves. One should verify the built-in check valve feature when shopping for the various types or styles of diffusers. Some have them some don't.

Bill,

I don't recall ever reading why a diffuser needs a check valve. I guess I assumed it was to keep water out of the air supply line so ice cannot form in the line at the iceline in the pond during winter; making it impossible to aerate during the winter. Is that the reason or is it something else?

Since we are talking air here, any thoughts on 24/7 during our winter months here in E Texas. With TFS in the pond, do you think it is wise to run air during the day and night and maybe cooling the water down to much for tfs survival. Year before last I saw 44 degree surface temp and last year I think it was 52. Any thoughts
Thanks

Check valves on diffusers are important to reduce chances of forming an ice plug in the airline and to reduce undue stress on the compressor at start-up especially if the system is cycled on-off. Some professional systems have two check valves; one on each diffuser and one at the compressor. If there is no check valve, water fills the airline when the compressor is off. At start up, the compressor builds extra high operating pressure (sometimes 3X normal) to push the water out of the airline. When air reaches the diffuser the pressure drops back to the normal operating psi. Excess pressure adds stress to the mechanics and over time shortens the life of the compressor.
A 3rd reason for a check valve is to reduce the chance of water draining or getting sucked back into the compressor during any off period. Water can drain back into the compressor for various reasons. Water in the compressor will damage or ruin the compressor. Water and excessive heat are the two main enemies of air compressors.

Thanks Bill. Sounds like a check valve for a diffuser is the way to go to me.