Pumps are used to move WASTEWATER to other parts of an ONSITE WASTEWATER TREATMENT SYSTEM. A pumping system consists of three key parts – the pump tank, the pump, and the controls. How the onsite system is designed to move WASTEWATER determines where the pump is located; and the location of the pump often impacts the sizing and appearance of the three components.

Pump tanks are used in several types of ONSITE WASTEWATER TREATMENT SYSTEMS, including dose to gravity, low-pressure distribution, subsurface drip distribution, and bio-filter systems. Each of these systems includes a pretreatment component, a pump tank, and soil treatment system. Dosing is the intermittent application of a set volume of WASTEWATER to the next component of the onsite system. Dosing to a gravity dispersal system or the use of pressure distribution help to spread WASTEWATER more evenly in the soil treatment area and promote better treatment. Dosing a bio-filter or other pretreatment component can achieve a high level of WASTEWATER treatment.

How a Pump and Pump Tank Works

A pump tank collects and stores WASTEWATER from the septic tank or other pretreatment component which is then dosed to the next component in the ONSITE WASTEWATER TREATMENT SYSTEM. It can be an individual tank or a separate compartment within a septic tank. The tank must be large enough to store the volume of WASTEWATER pumped during dosing, plus the minimum level of WASTEWATER needed for the pump to operate properly and a reserve capacity to allow time for a service call if the pump MALFUNCTIONS. Small pump basins are sometimes used; however, they have very limited emergency reserve capacity.

To minimize the amount of solids pumped to the next system component, the system must have some type of filter or screen. Options include an EFFLUENT screen in the sewage tank outlet, a filtered pump vault or screen basket to contain the pump, and/or a screen or disc filter in the pressure line.

A pump system can be dosed either on demand or by a timer. Demand dosing is a common method used for delivering WASTEWATER to soil treatment dispersal trenches. Timed dosing is more commonly used in systems that include subsurface drip dispersal or advanced pretreatment components. A pump tank contains:

• A pump, which pushes the water out of the pump tank and into the next component.
• A pump control float(s), which connects electric power to the pump when water in the tank reaches the set dosing level or to the pump control timer when there is enough water for a full dose. The same float or a second float disconnects the power when the water reaches the minimum water level.
• A high-water alarm float which is connected to an alarm to alert the homeowner to the high water condition. High water alarms usually indicate a pump MALFUNCTION, but may also indicate a clog in the pressure system, excessive water use, or a leak.

The pump must have the capacity necessary to deliver the WASTEWATER flow rate at the pressure required for system OPERATION. Each wastewater pump model has a relationship between flow rate and pressure, it is important to match the pump to the system.

In a demand dosed system, the pump operates when WASTEWATER fills the pump tank to activate the float set at the pump-on level. Dosing frequency depends on the amount of water used in the house or establishment. Each time the pump is activated, WASTEWATER is pumped until the low water level is reached. The volume of WASTEWATER delivered is determined by the float elevations and the tank size.

Timed dosing systems include an adjustable timer that controls the pump run time and rest interval. Using timed dosing instead of demand dosing spreads out peaks in WASTEWATER flow. Peak flows from the house or establishment are stored and then dosed evenly throughout the day. Sufficient surge capacity is needed in the pump tank to store the peaks and equalize the flow over the day to avoid nuisance high water alarms.

The high water alarm should have a buzzer and a visible light. Whenever the alarm is activated, contact your SERVICE PROVIDER to troubleshoot and repair the system. Conserve water until the system is repaired to prevent SEWAGE backup or overflow.

Design and Construction

Pump tanks are typically made of concrete, fiberglass, or plastic. Plastic tanks must be specifically approved for pump tank applications by the manufacturer. 

Pump tanks must be durable and watertight to prevent WASTEWATER from seeping out and groundwater from entering. Pump tanks must be located:

• On firm bedding material capable of bearing the weight of the tank and its contents;
• In an area easily accessible for the removal of liquids and accumulated solids; and
• To meet the set back distances specified in 19 CSR 20-3.060 Minimum Construction Standards for Onsite Systems.

The size or liquid capacity of a pump tank is based upon the minimum water level, the dosing volume, the surge volume in time dosed systems, and the emergency storage volume above the alarm level.

• The minimum volume is the level of WASTEWATER needed in the tank to cover the pump, if required by the pump manufacturer, or to cover the pump inlet.
• The dose volume is the amount of water delivered at one time. The dose volume is determined by the daily WASTEWATER flow from the house or establishment, the type and size of soil treatment component or other component being dosed, and the number of doses per day.
• The surge volume for time dosed system is based on peak flows and the flow equalization needed.
• The emergency storage volume is based on the daily flow from the house. In Missouri, regulations require a minimum emergency storage volume equal to the design daily flow.

Maintenance

Regular MAINTENANCE is essential to get the best performance from your onsite system. It is important that mechanical components in your system receive regular INSPECTION and MAINTENANCE. Pump tanks must be operated and maintained to minimize the chance of the system MALFUNCTIONING.

Inspections

INSPECTIONS must be conducted annually and as recommended by the manufacturer and include assuring:

• If applicable, the riser on the tank is in good condition and watertight;
• The lid on the tank or riser is locked or otherwise secured to prevent accidental entry;
• The liquid level of the tank has remained within acceptable levels;
• The SLUDGE level is managed at a level below the pump intake;
• The tank is in good condition with no evidence of leaks. A concrete tank is considered unacceptable if the rebar is visible or signs of rust from the rebar are evident; and a plastic tank is considered unacceptable if the tank is deformed so that the liquid volume is significantly reduced or the lids and/or riser can no longer be sealed;
• The pump, floats, and alarm are functional;
• Pump cycles properly and delivers correct dose rate and volume;
• Pump operates without excessive noise or vibration;
• Electrical connections are free of corrosion; and
• EFFLUENT screen is not clogged.

Pumping

It is the responsibility of the homeowner or user of the sewage tank system to schedule with a REGISTERED ONSITE WASTEWATER TREATMENT SYSTEM PROFESSIONAL or other qualified SERVICE PROVIDER for the removal and sanitary disposal of solids from the pump tank when the SLUDGE level exceeds seventy (70%) percent of the volume below the pump intake or if needed when any other tank or compartment is pumped.

The REGISTERED ONSITE WASTEWATER TREATMENT SYSTEM PROFESSIONAL or other qualified SERVICE PROVIDER is responsible for the proper treatment and disposal of all hauled WASTEWATER by transporting to a municipal sewage treatment plant capable of receiving the waste; transporting to a SLUDGE handling facility which possesses a current and valid permit issued for such activity; or land applying under a current and valid permit for such activity.

Servicing of Filter Screens

Sewage tank outlet EFFLUENT screens must be cleaned when the sewage tank is pumped or more often if needed;

Pump vaults or basket filters must be cleaned when the pump tank is pumped or more often if needed; and

Pressure line screen filters or disc filters must be cleaned every six months or as specified by the system designer or manufacturer. Alternatively, systems can be designed to automatically flush filters.

Final Treatment and Dispersal

Although properly operated and maintained septic tanks, aeration treatment units, and bio-filters are effective at providing treatment, WASTEWATER leaving the pump tank or pretreatment component must receive further treatment before it is ready to be returned to the environment. Methods for final treatment and dispersal include discharge to a soil treatment system or a lagoon.

Warning Signs of System Malfunctioning

While proper use, INSPECTIONS, and MAINTENANCE should prevent most pump and pump tank problems, it is still important to be aware of changes in your system and to act quickly if you suspect the system is MALFUNCTIONING. The most obvious onsite system failures are easy to spot.

• The alarm on the pump tank is activated;
• Surfacing SEWAGE, pooling water or muddy soil around your soil treatment system or in your basement;
• Plumbing or septic tank backups;
• Slow draining fixtures;
• Gurgling sounds in the plumbing system;
• SEWAGE odors in the house or yard;
• Localized overgrowth of lush green grass in or near the soil treatment area; and/or
• Tests show the presence of bacteria in well water.

Onsite systems fail when partially treated WASTEWATER comes into contact with groundwater. This type of failure is not easy to detect, but can result in the pollution of wells, nearby streams, or other bodies of water.

If you notice any of these signs, or you suspect your septic tank system may be having problems, contact a qualified SERVICE PROVIDER or the local onsite WASTEWATER ADMINISTRATIVE AUTHORITY for assistance.

Pump Tank Do’s and Don’ts

Proper OPERATION and MAINTENANCE of an onsite system can prevent costly repairs or replacement and can protect your property value. Observing the following recommendations will help to keep your system operating properly.

Do's

• Obtain the necessary permits from the appropriate ADMINISTRATIVE AUTHORITY before making any repairs.
• Use REGISTERED ONSITE WASTEWATER TREATMENT SYSTEM PROFESSIONALS and qualified SERVICE PROVIDERS.
• Conserve water to avoid overloading the onsite system, use high-efficiency fixtures and promptly repair any leaky faucets or toilets.
• Pump your pump tank at the same frequency as your septic tank or other pretreatment component. This may be the single most important thing you can do to protect your soil treatment system and your investment.
• Divert other sources of water, like roof drains, house footing drains, and sump pumps away from the soil treatment area.
• Landscape the system properly. Plant grass over and near the soil treatment system; roots from nearby trees or shrubs might clog and damage the system.
• Contact a qualified SERVICE PROVIDER if you experience problems with your system, such as surfacing WASTEWATER in your yard or other warning signs the system may be MALFUNCTIONING.
• Keep detailed records regarding the system, its location, make/model, contract service agreement, service visits, and MAINTENANCE performed.
• Use commercial bathroom cleaners and laundry detergents in moderation and only according to manufacturer’s directions.
• Keep your pump tank accessible for INSPECTIONS and pumping; yet locked or otherwise secured to prevent accidental entry.
• Have your private water well tested periodically or if you experience any warning signs of the system MALFUNCTIONING (contact your local public health agency).
• If your pump tank alarm is activated – contact your SERVICE PROVIDER promptly to repair the system and minimize your water usage in the interim.

Don'ts

• Don’t enter a pump tank or septic tank. Poisonous gasses or a lack of oxygen can be fatal.
• Your septic tank system is not a trash can. Don’t put dental floss, feminine hygiene products, flushable wipes, condoms, diapers, cotton swabs, cigarette butts, coffee grounds, cat litter, paper towels, paint, pesticides, or other hazardous chemicals into your system.
• Don’t use caustic drain openers for a clogged drain. Instead, use boiling water or a drain snake to open clogs.
• Don’t drive or park vehicles or allow livestock on any part of your septic tank system. Doing so can compact the soil in your soil treatment area or damage the pipes, tanks, or other onsite system components.
• Don’t build over any part of your septic tank system; this includes patios, carports, and other structures.
• Don’t attempt to pump your own pump tank or septic tank; use the services of a qualified SERVICE PROVIDER.