Remove the Bad Septic Odor From Your Home for About $100

What causes foul odors from septic systems to enter a home? A failed sink or toilet trap could be the cause. But older homes on slabs sometimes have failed J-shaped traps buried below the slab. Here are 7 easy steps to depressurize the system and clear the air.

During the long months of the Covid-19 lockdowns, my septic system odors became progressively worse. I noticed they would creep inside my home whenever I ran the kitchen range hood or turned on the dryer.

But also just randomly on hot days the odor would get bad. I was worried. It’s coronavirus world. How could I spend $10,000 on a new septic system, an alternative septic system, or a sub-slab excavation right now, when we don’t know yet if we’ll have an economy in two years?

But fresh air is a necessity, so I took a scientific approach. That usually works better than blind guesswork:

Step 1. Rule Out the Easy Stuff

Check the condition of your toilets. They have built-in traps that should prevent odors from re-entering.

I replaced one of mine that had a rusty ring and an ancient wax seal. I also checked the j-trap in my bathroom sink, and finally narrowed my search to look at the drain for my built-in shower. This ominous drain was my prime suspect, disappearing through the slab into some dark nether-region of old iron pipe, then beelining straight into the 600-gallon septic tank.

Step 2. Scope the Septic Situation

My next step was to see if the problem was a result of negligent septic system maintenance. If functioning properly, it shouldn’t stink much. Regardless of the type of septic system, liquid should seep away from the tank and into what’s called the leech field, or drain field.

My system, it turned out, is on its last legs. It will soon need replacing and is functioning as more or less a static cesspool at this point. Yuck. Thus the buildup of higher levels of unpleasant odors—too much for standard through-the-roof pipe venting to handle.

Step 3. Create Negative Air Pressure

Short of tearing out my septic and all of my old iron pipe, I seemed to have no affordable way to remove these bad septic odors. Or did I? What makes gas flow from one place to another? A difference in pressure.

If I could create enough negative air pressure in the house via one of the existing exhaust pipes, I could gain control over all of the fumes coming out of the tank, and counteract the negative air pressures inside the house (exhaust fans, vent fans and so on).

Step 4. Skip the Airflow Calculation

One problem I anticipated was that I’m not an engineer, so I had no idea how to calculate the exact airflow (in cubic feet per minute) required to depressurize my septic system and pipes without overdoing it. One risk might be that I could create a whooshing noise through my pipes, or make my toilets burble!

So I played it safe. I found a low-cost, wifi-controlled inline duct fan with a variable speed motor that you can control with a remote. It uses only 18 watts at full speed, and costs just under $80 online.

Step 5. Assembling the “Stench Ray”

I call my contraption a Stench Ray, because it looks like something from an old sci-fi movie, but of course it’s just a chimney with a fan in it. To make it work, and improve its moisture resistance, however, takes a little more tweaking.

I used clear 100 percent silicone caulking to waterproof every place where rain might get into the motor or wifi receiver. I also caulked between the fan and the stainless steel cap, and between the fan and the coffee can extender and the rubber coupler. Use three sheet self-drilling metal screws to attach the fan to the coffee can and three more to hold the cap on.

Note: Be sure to paint the coffee can with rust-inhibiting paint. Otherwise, it will oxidize way faster than you expect. It’s cheap tin.

Now drop the whole assembly onto your existing exhaust pipe. Before you tighten the bottom clamp and rig a permanent power source, test it with an extension cord.

Step 7. Optimize the Fan Speed

Now for the fun part. Turn on your dryer, your range hood, and your bathroom fan. Running all three is a worst-case scenario for pulling in septic gases.

Point the wifi remote control up through the ceiling in the general vicinity of your Stench Ray. Use your nose. Gradually increase the speed of the fan until your indoor air is odorless and clear again. With luck, you will barely hear the outdoor fan, and you have now pressure balanced your home so that you should never again smell septic odors indoors.

I must conclude with a caveat. My septic odor solution isn’t meant as a permanent fix for a faulty septic with failed plumbing. But compared to the cost and difficulty of putting in a septic during the pandemic, it’s a great, affordable workaround.

My low-cost fan idea will allow you to live safely in your home as you wait out the weeks or months of Covid-19 upheaval. I have no idea how long the mechanism will last when the winds and rain get fierce, but I’ve found that the concept works.

My septic odors went away the moment I turned it on, and you could always replace it down the road with a more expensive inline radon fan that’s designed to handle any weather.

Fan: $79

TerraBloom ECMF-100-R, Quiet 4" Inline Duct Fan with Wireless Remote Speed Controller

Cap: 24.94

The Forever Cap CCSSVENT 4-Inch Stainless Steel Plumbing Vent Cap

Coupler: 10.48

Spectre Performance 9741 Black 4" x 3.5" Intake Coupler

Coffee Can: 12 Oz.—Free (after you drink the coffee)