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Public Health - Seattle & King County

What to expect when the septic tank needs pumping

General recommendations

It is recommended to pump your septic tank every 3 - 5 years. How often you pump depends on the amount of water you use. General rule of thumb:

the more people using your septic system = increased water flow = your septic tank will fill up faster = more frequent pumping

More information about how your septic tank works. It may be possible that the septic tank will need pumping more often than 3 - 5 years.

Choosing your certified pumper

You should contact at least three certified Pumpers and select the pumper that best suits your needs. See list of certified pumpers. We suggest you locate your septic tank before calling the pumper. The following are recommended questions you should ask the pumper about their services:

  1. What is the cost of the pump-out?

  2. If the septic tank is over 1,000 gallons, will extra gallons cost extra?

  3. Does this cost include digging to uncover the septic tank lid(s)?
    1. If not, do you charge by the foot?
    2. If not, how much do you charge to dig out:
      • 1 septic tank lid
      • 2 septic tank lids
      • Pump tank lid (if you have one)
  1. Does the cost include dumping fees?

  2. Does this cost include inspection of the inlet and outlet baffles in the septic tank?
    1. Do you charge extra to clean the filter baffle?

  3. Is there an additional charge for the extra water and time required to pump a tank that has not been maintained properly (for example, pumped on a regular basis)?

  4. If you have a long distance to pump or will require pumping up a steep slope, provide the distance and elevation to where the Pumper's truck will be located (for example, in your driveway or in the yard). The Pumper will determine if the truck can provide this type of service.

  5. Is pumping the pump tank part of your regular service? What is the charge for this service?
    If there is a pump tank, it should be pumped in addition to the septic tank, rinsed with a hose, and pumped dry. If the pump tank is very full, you may be charged an extra fee.
Locating the septic tank

Once you make a decision on a Pumper, you will need to find the septic tank. Most Pumpers will charge you for locating the tank and uncovering the septic tank lid(s). You can do the labor yourself to expose the septic tank lid(s) before the Pumper arrives.

Public Health - Seattle & King County recommends that you have "risers" installed to make the septic tank pumping and inspection visits easier and less time-consuming. A riser has locking gas tight lids attached to the tank with access brought to the surface so there is no digging each time the septic tank is pumped. It makes pumping and inspections cause less mess and disruption in your yard. Most septic system Pumpers will be able to provide this service.

If you have a 2-compartment tank (houses built from 1975 to present have 2-compartment septic tanks), you will need to uncover both tank covers. Both compartments are required to be inspected and pumped. If the second compartment goes without pumping, it will eventually fill with solids and create problems.

If there is an as-built (a map of your septic system) for your septic system, locating the septic tank will be easy to do. Search and download a copy of your as-built drawing. If an as-built is not available, you or your Pumper need to use some investigative skills:

  • If there is a crawl space, you may determine where the plumbing leaves the foundation wall, then use a probe bar to find the tank. If you have a fiberglass or polyethylene tank, a probe bar is not recommended unless extreme caution is observed. Probing will only work if the tank is not more than 1 to 2 feet under the surface.

  • If no crawl space is available you can sometimes go by where the plumbing vents are located in the roof. If one is behind the house and coming from a bathroom, this may line up with the exit point of the sewer line leading to the septic tank.

If these options don't work, it may be necessary to use an electronic detection device. Some rental services have a transmitter that can be flushed down a toilet which can be detected with a receiving unit. Some septic system Installers specialize in locating drainfields. See list of certified septic system Installers.

While the tank is uncovered, sketch a map of the septic tank lid(s) location in relation to the house and record the map for your files. Photos of the area, including the house, can also be valuable for future pumping.

Pumping the septic tank

Before the Pumper begins the process of pumping out the tank, you may ask him to measure the scum and sludge layer thickness. By doing this, you can judge the rate at which the solids accumulate in the tank which will help you decide when you should have the septic tank pumped next. Most households will fall in the 3 to 5 year range for pumping frequency. Regardless of the pumping frequency that is used, the regular inspections of your septic system will provide assurance that all is well within these tanks. About inspecting your septic system.

The septic tank Pumper should provide you with a receipt detailing the service that was provided. This receipt should include:

  • Name, address, phone number of company
  • Name of certified Pumper
  • Approximate number of gallons that were pumped
  • Number of compartments pumped
  • Condition of the tank baffles
  • Condition of the septic tank
  • Details on any work done to baffles or access lids. If scum and sludge layers were measured, they should be recorded on the pump receipt
  • Details on any work done on the septic tank or pump tank
  • Any other service work done