Air Diffuser Sizing

Proper sizing of air diffusers, hoses and fittings can enhance aeration efficiency and increase pump service life.

Following table estimates the quantity of each diffuser model that can be utilized with the air pump.

(Primary Reference: Pump)
Pump
Model
Pressure
Load
Equivalent
Depth
#3
Output
Capacity
Sintered Airstone EPDM Membrane Diffuser
4" D 6" L 9" L 12" L 7" D 9" D 11" D
 
AL-40 1.4 PSI < 3.2 ft w.c. 1.8 CFM 9 ~ 10 6 ~ 8 3 ~ 4 2 ~ 3 2 * 2 * 1 *
2 PSI < 4.6 ft w.c. 1.6 CFM 7 ~ 8 5 ~ 7 3 ~ 4 2 ~ 3 2 1 ~ 2 1
3 PSI < 6.9 ft w.c. 1.3 CFM 6 ~7 4 ~ 5 2 ~ 3 2 1 1 1
 
AL-60 1.4 PSI < 3.2 ft w.c. 2.4 CFM 12 8 ~ 10 4 ~ 6 4 * * *
2 PSI < 4.6 ft w.c. 2.2 CFM 11 7 ~ 9 4 ~ 5 3 ~ 4 2 ~ 3 2 1 ~ 2
3 PSI < 6.9 ft w.c. 1.8 CFM 9 6 ~ 8 3 ~ 4 2 ~ 3 2 1 ~ 2 1
 
AL-80 2 PSI < 4.6 ft w.c. 3.0 CFM 15 9 ~ 13 5 ~ 7 4 ~ 5 3 ~ 4 2 ~ 3 2
3 PSI < 6.9 ft w.c. 2.0 CFM 10 6 ~ 8 4 ~ 5 3 2 ~ 3 2 1
 
AL-100 2 PSI < 4.6 ft w.c. 4.0 CFM   13 ~ 17 7 ~ 10 5 ~ 7 4 ~ 5 3 ~ 4 2 ~ 3
3 PSI < 6.9 ft w.c. 3.5 CFM   11 ~ 15 6 ~ 8 4 ~ 6 3 ~ 5 2 ~ 4 2
4 PSI < 9.2 ft w.c. 2.9 CFM   9 ~ 12 5 ~ 7 4 ~ 5 3 ~ 4 2 ~ 3 2
 

AL-120

2 PSI < 4.6 ft w.c. 5.1 CFM   16 ~ 21 9 ~ 12 6 ~ 9 5 ~ 7 3 ~ 5 3
3 PSI < 6.9 ft w.c. 4.4 CFM   14 ~ 18 8 ~ 10 6 ~ 7 4 ~ 6 3 ~ 4 3
4 PSI < 9.2 ft w.c. 3.5 CFM   11 ~ 15 6 ~ 8 4 ~ 6 4 ~ 5 2 ~ 3 2
 

AL-150

2 PSI < 4.6 ft w.c. 6.7 CFM   21 ~ 28 12 ~ 16 8 ~ 11 7 ~ 9 4 ~ 7 3 ~ 4
3 PSI < 6.9 ft w.c. 5.8 CFM   18 ~ 24 10 ~ 14 7 ~ 10 6 ~ 8 4 ~ 6 3 ~ 4
4 PSI < 9.2 ft w.c. 4.6 CFM   14 ~ 19 8 ~ 11 6 ~ 8 5 ~ 6 3 ~ 5 2 ~ 3
 

AL-200

2 PSI < 4.6 ft w.c. 8.8 CFM   28 ~ 36 16 ~ 21 11 ~ 15 9 ~ 12 6 ~ 9 4 ~ 6
3 PSI < 6.9 ft w.c. 7.4 CFM   23 ~ 31 13 ~ 18 9 ~ 12 7 ~ 10 5 ~ 7 4 ~ 5
4 PSI < 9.2 ft w.c. 6.0 CFM   19 ~ 25 11 ~ 14 8 ~ 10 6 ~ 8 4 ~ 6 3 ~ 4
 

AL-250E

2 PSI < 4.6 ft w.c. 9.5 CFM   30 ~ 40 17 ~ 23 12 ~ 16 10 ~ 13 6 ~ 10 5 ~ 6
3 PSI < 6.9 ft w.c. 8.8 CFM   28 ~ 36 16 ~ 21 11 ~ 15 9 ~ 12 6 ~ 9 4 ~ 6
4 PSI < 9.2 ft w.c. 7.0 CFM   22 ~ 29 13 ~ 17 9 ~ 12 7 ~ 9 5 ~ 7 4 ~ 5
* Depth too shallow or inefficient for large area

 

Estimate based on [CFM/unit] 0.2 / disc 0.06 ~ 0.08 / inch length 0.75 ~ 1.5 / disc
Diameter (D)
Length (L)
1.2" D disc
Connection Fitting Size: 3/16" barb 1/4" barb, 1/2" MPT, 1" spigot 3/4" MPT

 

(Primary Reference: Pressure Load)
Pressure Load
Equivalent Depth #3
Pump
Model
Output
Capacity
Sintered Airstone EPDM Membrane Diffuser
4" D 6" L 9" L 12" L 7" D 9" D 11" D
1.4 PSI
< 3.2 ft w.c.
AL-40 1.8 CFM 9 ~ 10 6 ~ 8 3 ~ 4 2 ~ 3 2 * 2 * 1 *
AL-60 2.4 CFM 12 8 ~ 10 4 ~ 6 4 * * *
                   
2 PSI
< 4.6 ft w.c.
AL-40 1.6 CFM 7 ~ 8 5 ~ 7 3 ~ 4 2 ~ 3 2 1 ~ 2 1
AL-60 2.2 CFM 11 7 ~ 9 4 ~ 5 3 ~ 4 2 ~ 3 2 1 ~ 2
AL-80 3.0 CFM 15 9 ~ 13 5 ~ 7 4 ~ 5 3 ~ 4 2 ~ 3 2
AL-100 4.0 CFM   13 ~ 17 7 ~ 10 5 ~ 7 4 ~ 5 3 ~ 4 2 ~ 3
AL-120 5.1 CFM   16 ~ 21 9 ~ 12 6 ~ 9 5 ~ 7 3 ~ 5 3
AL-150 6.7 CFM   21 ~ 28 12 ~ 16 8 ~ 11 7 ~ 9 4 ~ 7 3 ~ 4
AL-200 8.8 CFM   28 ~ 36 16 ~ 21 11 ~ 15 9 ~ 12 6 ~ 9 4 ~ 6
AL-250E 9.5 CFM   30 ~ 40 17 ~ 23 12 ~ 16 10 ~ 13 6 ~ 10 5 ~ 6
                   
3 PSI
< 6.9 ft w.c.
AL-40 1.3 CFM 6 ~7 4 ~ 5 2 ~ 3 2 1 1 1
AL-60 1.8 CFM 9 6 ~ 8 3 ~ 4 2 ~ 3 2 1 ~ 2 1
AL-80 2.0 CFM 10 6 ~ 8 4 ~ 5 3 2 ~ 3 2 1
AL-100 3.5 CFM   11 ~ 15 6 ~ 8 4 ~ 6 3 ~ 5 2 ~ 4 2
AL-120 4.4 CFM   14 ~ 18 8 ~ 10 6 ~ 7 4 ~ 6 3 ~ 4 3
AL-150 5.8 CFM   18 ~ 24 10 ~ 14 7 ~ 10 6 ~ 8 4 ~ 6 3 ~ 4
AL-200 7.4 CFM   23 ~ 31 13 ~ 18 9 ~ 12 7 ~ 10 5 ~ 7 4 ~ 5
AL-250E 8.8 CFM   28 ~ 36 16 ~ 21 11 ~ 15 9 ~ 12 6 ~ 9 4 ~ 6
                   
4 PSI
< 9.2 ft w.c.
AL-100 2.9 CFM   9 ~ 12 5 ~ 7 4 ~ 5 3 ~ 4 2 ~ 3 2
AL-120 3.5 CFM   11 ~ 15 6 ~ 8 4 ~ 6 4 ~ 5 2 ~ 3 2
AL-150 4.6 CFM   14 ~ 19 8 ~ 11 6 ~ 8 5 ~ 6 3 ~ 5 2 ~ 3
AL-200 6.0 CFM   19 ~ 25 11 ~ 14 8 ~ 10 6 ~ 8 4 ~ 6 3 ~ 4
AL-250E 7.0 CFM   22 ~ 29 13 ~ 17 9 ~ 12 7 ~ 9 5 ~ 7 4 ~ 5
* Depth too shallow or inefficient for large area

 

Notes:

  1. Type and quantity of air diffuser required varies with application.
    For most aeration purposes, deploy as many air diffusers or have as much diffusing surface area as possible.

  2. Air escapes through path of least resistance, size and utilize air manifold properly to balance or distribute air flow between diffusers at different distances and depths (different levels of resistance). Bleed off any excess volume, DO NOT forcibly reduce the overall pump output. Improper flow regulation will introduce long term over pressure and high thermal stresses to significantly reduce the diaphragm service life.

  3. Equivalent depth in foot of water column (w.c.) assumes zero loss (no resistance) in the air distribution channels. However, actual work load (back pressure) at depth of 4.6 ft w.c. for example can be greater than 2 PSI due to total air resistance from diffusers, hoses, valves, fittings and supplied air flow rate, etc.

  4. With good air ventilation and proper sizing of air tubing and connection fittings, insufficient quantity of air diffusers may not be detrimental to the air pump. However, forcing high air flow rates through limited diffusing surface area generally produces larger size air bubbles that have lower overall bubble surface area and faster rise time. The resulting aeration efficiency will be low or poor.

  5. Good air ventilation means there must be air movement around the pump housing either naturally from wind or mechanically by fan to promote rapid heat dissipation. Keeping internal parts running cooler will help to ensure more durable and reliable pump operation. Temperature controlled room, randomly positioned vents or ample of open spaces do not guarantee rapid heat dissipation.

  6. Replace old clogged air diffusers and clean air manifold periodically. Clogged diffusers reduce efficiency and cause pump to overheat from higher working pressure load, leading to shorter diaphragm service life.

  7. Do not use highly resistive air diffuser designed to produce micron size air bubbles (< 0.5 mm, < 500 μm, or < 0.02 in) with any linear diaphragm or linear piston pumps. Rocking piston or rotary vane compressors are more suited for higher pressure loads as they have much wider working pressure ranges and reduction in flow rate as pressure increases.