Vent or wye to prevent suspect drainage field from overflowing septic tank?

[Jeremiah Mercier]

I'm about to have a septic tank installed to replace a particularly old system. I plan to reuse the existing drainage field, which checks out for now, but the house sat vacant for 18 months so the field is highly suspect. If it fails I'll have to replace it, but I'd like to save the expense if I can avoid it. My biggest concern is that if the field fails the septic tank will back up and overflow into the house. Can I install a vent or wye or cleanout between the septic tank and drainage field so that if it backs up, it overflows after the septic tank (into the yard) rather than backing up into the house?

Here's a rough diagram:



The house is built on a slab. There's a vertical drop of several feet from the exit of the (to-be-installed) septic tank to the beginning of the drainage field. I didn't draw this very well. The drainage field is on a hill. This configuration seems ideal for installing some kind of overflow vent since I could easily install the vent above the start of the drainage field but below the exit from the tank. Then as long as the field is functioning the vent would remain clear, but if the field fails, it would overflow the vent without affecting the septic tank or house.

I realize allowing effluent to overflow into the yard is very unsanitary, but I'm pretty sure overflowing raw sewage into the house is less sanitary. What is the "right" way to do this? Is anything like this permitted by plumbing codes? Plumbing codes aside, what is the most practical way to do this?

 

[breplum]

You should absolutely have two sets of cleanouts with pop-off caps to allow sewage back-ups outside the dwelling.
Within a few feet of the house and then wherever is appropriate past the septic tank.
Two-Way Cleanout fittings is what they are called.
These are the ones we prefer

 

[breplum]

You can use the cheaper ABS ones but most sewer guys like the distinctive ability to go either direction.
Here is a good way to protect the cleanouts and also prevent mischeif:

 

[Jeremiah Mercier]

Thank you!