Hydraulic Load Test
What is a “Hydraulic Load Test” and when is it required?
A hydraulic load test is used to determine if a septic system’s absorption area (drain field, sand mound, seepage pit, etc.) is able to handle the PA-DEP specified daily volume, which is 400 gallons per day plus 100 gallons for each bedroom over three. It is required any time the absorption area is not receiving normal usage on a daily basis. If the house served by the septic system is occupied and in normal use, the absorption area is evaluated by the way it reacts to the load imposed by the occupants. However, if the house is not occupied and in normal use, there is no load on the absorption area and a hydraulic load test is needed to verify that it is functioning satisfactorily.
How is a Hydraulic Load Test performed?
A hydraulic load test requires two days to complete. On Day 1, the technician measures and records the water level in the absorption area (drain field, sand mound, seepage pit, etc.) and then begins adding clean water. Water is added until the absorption area reaches its maximum capacity or the full PA-DEP specified daily volume is introduced. The technician then measures and records the water level in the absorption area again.
On Day 2, after the system has had 24 hours to absorb the water introduced on Day 1, the technician returns and measures the water level in the absorption area. In order to determine how much water was absorbed during the previous 24 hours, the technician again adds clean water to the system until the water level reaches the “high point” from Day 1 or until the full PA-DEP specified volume is introduced. The amount of water added on Day 2 is the amount of water absorbed during the 24 hour test.
Can a Hydraulic Load Test harm the septic system?
No. Since water is only added until the system reaches it’s maximum capacity, or until the PA-DEP specified daily volume is introduced, whichever is less, there is no chance of harming the septic system.