Pressure Distribution System
Also called: pressurized septic system, low-pressure pipe system, LPP system
A pressure distribution system uses a pump to deliver timed, even doses of effluent through a network of small-diameter pressurized pipes to the drain field. Unlike gravity systems that allow continuous flow whenever effluent is available, pressure distribution ensures each section of the drain field receives a measured, uniform dose followed by a rest period - improving treatment efficiency and reducing the risk of overloading any single area.
Pressure distribution systems vary significantly in pump size, lateral spacing, dose volume, and timer settings based on site conditions and county design standards. Timer and pump settings are specific to each installation. Ask the county health department who may adjust them. Requirements for maintenance agreements, inspection frequency, and reporting vary by county.
How It Generally Works
1Primary treatment in the septic tank
Wastewater enters the septic tank where solids settle and scum floats, leaving clarified effluent in the middle layer - identical to the first stage of a gravity system. The effluent filter at the outlet helps protect the downstream pump from solids.
2Effluent moves to the pump chamber
Clarified effluent flows from the septic tank into a pump chamber (dosing tank). A submersible pump and float switches control when and how much effluent is delivered. When the liquid level in the pump chamber rises to the trigger float, the pump delivers a set volume of effluent to the drain field.
3Pressurized delivery through the lateral network
The pump forces effluent under pressure through a manifold and into a network of small-diameter perforated lateral pipes. The holes in the laterals are sized so that effluent discharges simultaneously and evenly along the entire length of each lateral - distributing the dose across the full drain field area rather than concentrating it at the inlet end.
4Dosing rest cycle
After the dose is delivered, the pump stops and the drain field receives a rest period before the next dose. This allows the soil to absorb and treat the previous dose before new effluent arrives, which is especially important on sites with slower-draining soils.
Common Maintenance Considerations
Pump and float inspection
The dosing pump and float switches should be inspected periodically - typically at each pump-out - for wear, corrosion, and proper float operation. Pump failure stops effluent delivery entirely and activates the alarm.
Lateral flushing
Mineral deposits and biofilm can accumulate inside the pressurized laterals over time. Flushing the laterals (opening end caps and running the pump briefly) is a maintenance task on many pressure distribution systems. The frequency depends on the system design and local water chemistry.
Alarm system function
The control panel alarm must be operational at all times. Regular visual checks of the panel - verifying the green power light is on and no alarm condition is active - help catch problems early. A failed alarm means a pump problem may go unnoticed.
Tank pumping
The septic tank still accumulates sludge and scum and requires periodic pumping, regardless of how well the pump chamber and laterals are functioning. The tank pump-out interval depends on household size and use.
Observable Conditions to Share for Service Planning
The following are observable conditions, not remote diagnoses. General Septic can assess the system on site as part of the requested service.
Pump alarm activation
An active alarm at the control panel indicates the liquid level in the pump chamber has risen above normal - typically because the pump is not running or is unable to keep up. Reduce household water use immediately and describe the request to General Septic.
Uneven or wet areas over the drain field
If one zone of the field is wet while others remain dry, there may be an uneven pressure problem - a blocked lateral, a lateral with failed emitter holes, or a manifold issue. Even distribution is central to a pressure system's design; deviation is a diagnostic signal.
No pump sounds during expected dosing cycles
On systems where pump cycles are audible from inside or near the pump chamber, an absence of pump operation may indicate pump failure, a tripped breaker, or a float stuck in the off position.
System Details to Include in a Request
Having this information ready helps General Septic plan the requested service:
- Whether the alarm is currently active
- How long the system has been in its current state
- The pump brand and model, if visible on the control panel
- Timer or dose volume settings, if known
- When the tank was last pumped and laterals last flushed
Related Services
Describe a request in the greater Seattle area
General Septic directly provides septic services across King, Pierce, and Snohomish counties with its staff and equipment. Describe your system and situation in the request form so the team can plan the work.