Septic tank that never needs pumping?

[Mikey]

A friend has had his OSS back up into the house 2 times in the last two years. The first of these was blamed on a missing baffle, and a T was installed somewhere to substitute. The most recent was caused by a huge wad of toilet paper that clogged the new T. But that may be irrelevant -- I asked them when the tank was last pumped, and they said it never needed pumping. It's been in service 18 years now, and I'm guessing that's just about how long it takes scum & sludge to meet.

Has anyone ever heard of a never-pump system? It seems to me to fly in the face of everything I've learned about septic systems -- anaerobic or aerobic. Overall, it looks like a conventional pump-to-gravity system, except it pumps up to a sand filter, which then drains by gravity back down to the leach field, which is next to the septic and pump tanks. Bottom line, is it all starts at what looks like a conventional septic tank, which their builder claimed never needed pumping, and they believed him. Am I missing something?

 

[Ryan]

There is no such thing as a septic tank that never needs pumping. The primary reason you have a septic tank in the first place is to hold all the solid waste coming out of the house. The reason he had an issue previously when you mentioned the baffle or the T is because the outlet T keeps the solids from going out of the tank and stopping any liquid from exiting the tank. Im not sure what area you are located however from most 2 bathroom homes with a family of 4 you should have the tank pumped about every 4 or 5 years. that time is reduced if you have a lot of people or rent the home out. Feel free to ask me if you have any more questions.

 

[Mikey]

"There is no such thing as a septic tank that never needs pumping." ... That's what I thought.
"the outlet T keeps the solids from going out of the tank" ... His missing baffle was on the inlet side. That baffle keeps the scum layer from backing up into the inlet pipe.
"what area you are located" ... We're in NW Washington state. Pumping is only required when the annual inspection demands it. I suspect the inspections were cursory.

He's getting in touch with the engineer that designed the system. I'll let you know what they determined, if he ever shares...

 

[Ryan]

Yea am engineered system is much more complicated then your conventional gravity flow system but the tank would still have to be pumped. What are or location is your friends property located?

 

[Mikey]

We're in Kitsap County, WA.