CALCULATE PRESSURE DROP

Method to calculate pressure drop for aeration systems
John Morris - 15Jan04

When multiple diffusers are attached to the same pump, the pressure drop will depend on the diffuser that is furthest and/or deepest, i.e., the path of greatest resistance. The manifold valving will adjust the pressure drop to each diffuser to be the same as the one with the greatest resistance so that each diffuser will get the same flow. If one diffuser is deeper than one that is farther away, then calculate the pressure drop for both and choose the greatest.

1. Determine the number of CFMs per diffuser.

2. Determine the hydrostatic head (psi) by dividing the diffuser depth by 2.31.

3. Determine the friction loss from the table below based on the number of CFMs per diffuser and hose size. The value in the table is for 100 ft; multiply or divide appropriately to adjust for the length in the specific application.

4. The total pressure drop for the system is the sum of the hydrostatic head plus the friction loss, plus 1.0 psi for the diffuser/check valve assembly.

Pressure drop per 100 ft of hose in Pounds per Square Inch (psi)
Hose i.d. - inches

CFM	0.375	0.5	0.625	0.75	1	1.25	1.5	2	3	4
1	0.26	0.077	0.021	0.008	0.002	0.001	0.0003	0.0001	0.0000	0.0000
2	1.01	0.30	0.085	0.032	0.008	0.003	0.001	0.0003	0.0000	0.0000
3	2.24	0.66	0.19	0.073	0.018	0.007	0.003	0.001	0.000	0.000
4	3.94	1.16	0.34	0.13	0.033	0.013	0.005	0.001	0.000	0.000
5	6.09	1.80	0.52	0.21	0.052	0.020	0.008	0.002	0.000	0.000
6	8.71	2.57	0.75	0.30	0.076	0.030	0.012	0.002	0.000	0.000
7	11.8	3.48	1.03	0.41	0.10	0.041	0.017	0.003	0.000	0.000
8	15.3	4.52	1.34	0.54	0.14	0.054	0.022	0.004	0.001	0.000
9	19.3	5.69	1.69	0.69	0.18	0.069	0.028	0.005	0.001	0.000
10	23.7	7.00	2.08	0.85	0.22	0.086	0.035	0.007	0.001	0.000
12	33.9	10.00	3.00	1.23	0.32	0.13	0.052	0.010	0.001	0.000
15	52.4	15.5	4.67	1.95	0.51	0.20	0.082	0.015	0.002	0.001
20	92.1	27.2	8.28	3.49	0.93	0.37	0.15	0.027	0.004	0.001
25	142.5	42.1	12.9	5.51	1.48	0.58	0.24	0.042	0.006	0.001
50	553.9	163.6	51.3	22.6	6.27	2.46	1.01	0.169	0.023	0.006
75	1225.5	362.0	114.9	51.6	14.6	5.72	2.34	0.381	0.050	0.013
100	2152.8	635.9	203.7	92.6	26.5	10.4	4.26	0.677	0.088	0.023
125	3332.7	984.5	317.6	145.9	42.2	16.6	6.78	1.058	0.135	0.035
150	4762.9	1406.9	456.5	211.5	61.7	24.2	9.91	1.523	0.193	0.051
175	6441.5	1902.8	620.4	289.5	85.0	33.4	13.7	2.073	0.261	0.069
200	8367.0	2471.5	809.2	380.0	112.3	44.1	18.0	2.708	0.338	0.090

*THE QUALITY OF THE WATER REFLECTS THE QUALITY OF MANAGEMENT*