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I'm finding that I need more aeration for my aquaponics fish tanks than is practical to supply by buying small consumer-grade air pumps for each tank. Additionally, typical consumer pumps have issues developing enough pressure to bubble air from an outlet that is under 4-6 feet of water. The water is simply too heavy for the tiny pump to overcome. Most aquarium pumps reach about 2-5 PSI.

I've considered using a small and quiet portable air compressor, like the type you might use to run a single pneumatic tool. These typically develop about 120-140 PSI and would have more than enough air flow to handle everything I need. The issue is that the only real affordable and easy to work with pipe, is plastic (PVC). PVC, as I understand, is not to ever be used for pressurized air lines owing to the fact that if it does fail, it fails catastrophically and dangerously, exploding into shards of plastic like a grenade.

Would applying a safety factor to the maximum PSI in the PVC lines allow me to safely use PVC? I've considered using a regulator to limit the pressure in the line to something safer, like 30 to 40 PSI, combined with a calibrated pressure relief valve that would vent the system if the pressure exceeded 50 PSI.

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    Compressors used for air tools are rarely quiet, even the "small" ones. You could, of course, put the pump somewhere else and run a long air hose. To answer your question, the usual solution when they develop more pressure than is needed is a buffer tank an a regulator (usually part of the package) ... and "real" air hose and fittings are cheap enough that I wouldn't bother with PVC for that purpose. – keshlam Jul 24 '15 at 19:57
  • What about an airbrush compressor? They should be a lot quieter, right? – cathode Jul 24 '15 at 20:26
  • Should be, but i don't know what output specs are for those. – keshlam Jul 24 '15 at 20:34
  • There are other tubings which are far more suitable for air transport - any standard air hose is the simplest. Tygon also works dandy for fishtank pressures. As for the compressor, for 30 years or more the "big fishtank compressor of choice" is to buy (new at the parts store, or used at the junkyard) an A.I.R. pump (smog pump) for a car, and belt it to a small electric motor - that has a much better pressure/volume fit to what fishtank air systems need, and is also relatively quiet. – Ecnerwal Jul 24 '15 at 20:50
  • So, 175 PSI in 480 PSI pipe should be perfectly safe, you're thinking: diy.stackexchange.com/questions/37538/is-a-pvc-union-air-tight/… – Ecnerwal Jul 25 '15 at 2:22
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Would applying a safety factor to the maximum PSI in the PVC lines allow me to safely use PVC?

Yes it probably would, as long as this is a personal project at your home or property. If this is in a workplace then it is likely you would be breaking the law by using unprotected PVC.

I would regulate it to no more than what is necessary to provide desirable results and set over-pressure protection at that setting as well. Also affecting safe use are factors such as UV degradation of the plastic (by sunlight and/or artificial light), placement where it could be struck/damaged while in use, etc. ANSI says max pressure is 100 psi, and that's for underground systems and above ground systems that are "protected".

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  • Thanks. I suppose regular foam pipe insulation should be enough to protect the pipe from UV rays although I doubt it would be considered "protected" from physical damage. – cathode Jul 24 '15 at 20:25
  • That's right, ANSI used "conduit", "steel" and "concrete" as examples of "protection". I feel that wrapping pipe insulation and securing with zip ties would (arguably) be a way of preventing flying shards in the very unlikely even of this "catastrophic pipe explosion" that seems to be the cause of concern. – Jimmy Fix-it Jul 24 '15 at 21:51
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Using an air compressor to provide air is solving the wrong problem.

There is something else wrong with your setup, such as a significant line losses in your tubing. 2 psi is enough to raise water over 4 feet, 5 psi should give you 11 feet of head.

1 atmosphere of pressure, about 14 psi, is about 33 feet of head, which is way more than what you're dealing with. You don't need 30 or 40 psi of pressure in your system, you'll instead want 5-10.

Workshop compressors are loud and expensive, and require frequent attention to deal with water that builds up in the tank. Instead, get a beefier pump that delivers enough pressure and volume, or get a small blower that is capable of generating enough dynamic pressure, such as a cheap electric leaf blower, run on low so it's not too loud.

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  • I see what you're saying, but you neglected to consider that backpressure significantly reduces flow. You can't aerate a 2700 gallon tank that is 5 feet deep with a pump that only puts out 2psi because when the pump is fighting against that much water pressure, it's flow rate drops to virtually nothing. this isn't theory i'm describing -- it's what I'm actually experiencing. – cathode Jul 24 '15 at 20:20
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    @cathode: it doesn't matter whether your tank is 1 gallon or a million, the only thing that matters is the depth. You must have significant line losses in your setup such as numerous valves, narrow diameter tubing, or other restrictions that dissipate energy. – whatsisname Jul 24 '15 at 20:29
  • true, water column back pressure is strictly due to height of water, not volume. Think of it as 1/2 psi per foot of water height. – Jimmy Fix-it Jul 24 '15 at 21:55
  • The math is essentially irrelevant here. The point is not to ensure that a few bubbles can show up at the specified depth. The point is that a sufficient volume of air needs to be delivered to aerate 2700 gallons of water. And a consumer aquarium air pump cannot achieve this. – cathode Jul 25 '15 at 7:59

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