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Pipe Size for Air Loop

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I purchased a used Jehmco pump that came with pieces of 3/4 pipe with air valves already drilled in. I will need to purchase new PVC to do my air loop. I just wanted to know if I am better going with 3/4 or 1" PVC for the loop. The pump is the same size as the Co-Op one and I know they said you can do 3/4 or 1 but I am not sure why one is better than the other. I plan to have around 12 - 15 drops in my fish room and the run will be around a 15' long x 8' wide for the loop. If I use the 3/4 I can use some of the pieces I got with the pump but if 1" is better I can just remove the valves and add them to the 1" without much issue. 

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I can speak to a general nature on plumbing but not to your specific set up.  

larger pipe means less frictional losses through it and in the case of a compressible gas, acts like a buffer tank.  Ie 1 inch pipe has roughly twice the volume of 3/4 pipe and frictional losses are roughly half iirc.

I would not be so concerned to replace 3/4 air valves for 1 inch. You could simply get 3/4 to 1 inch adapters that go after the valves.

my gut feeling is that the dimensions and drops you are looking at 3/4 would be fine with plenty of excess capacity,  but I have to admit to not being terribly familiar with required calculations.  It is just a gut feeling…



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I think the main benefit of having at least part of the loop in the larger size is buffering against vibration. I'm using the wrong words, but you'll get less pulsing or hammering with a larger diameter, due to the larger volume of air in the system. I use 1", am very happy with it. Some parts are 3/4, ie the connection between the pump and the loop, plus a "spur" that goes through the rear wall of the house to supply air to my bucket-ponds. 

DO include a few tees or valves for pressure relief, if you're not running too many outlets. Eg I have the Alita 40, and it runs say 15-25 sponges/stones/etc, and I have a couple extra valves fully open to reduce pressure in the system, hope it will prolong the life of my pump. The open valves tend to hiss, I've found that wrapping them in an old towel helps, so does running a LONG piece of tubing from them (like 10ft). And it lets you put the hissy opening somewhere out of the way. 

I suspended the loop in my basement from the ceiling using wire straps, but if (when) I redo it, I'll likely clamp it right to the joists. I was originally afraid the vibration would come through the floor, but the vibration in the loop is insignificant compared to the pump on the shelf, and I don't feel that so I think I'm safe. 

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