Do Both Septic Tank Caps Need Risers?
Wondering if you need risers on both septic tank caps? Learn why pumpers often use one side and when adding a second riser is helpful.
Septic systems often have two access points on top of the tank. One cap covers the inflow side where the pipe from the house connects. The other cap covers the outflow side, which usually includes the effluent filter and outlet pipe.
In this case, the septic company always pumps from the outflow side, where the effluent filter is located. That cover was fitted with a 24” Polylok riser to make pumping easier. The inflow side cover, which reveals the house line, has never been excavated. This raises two common questions from homeowners: why only use one access point, and should both sides have risers?
Question:
Why doesn’t the septic company use the input side cover, and should I install a riser on that side too?
Answer:
Pumpers often use only the outlet side because it gives direct access to the effluent filter and outlet pipe, where most solids settle. In many cases, one access is enough for a complete pump-out. However, best practice is to pump from both access points to ensure all solids are removed. Adding a riser to the inlet side is recommended for easier inspections, cleaning, and to meet some local code requirements. While not always required, it can extend the life of your system and save labor costs in future service calls.
Installing risers on both covers makes future maintenance faster and avoids unnecessary digging. It also allows for easier inspection of the inflow side for blockages or backflow issues.
For more guidance, check this EPA guide to septic system care. You can also review this detailed article on septic tank covers.
I’m Chris Mayer, writing for Plumbing 101.
