How to Flush Transmitters Effectively

The AT-12/ATP-12 or FT-8/FTP-8 transmitters are small enough to pass though 3 inch lines. You can free-flush it through the plumbing to the tank or to the blockage, whichever comes first. When you open the tank, the transmitter with its bright flashing LED should be found floating near the inlet baffle. Once retrieved, turn it off so you can use it on the next job.

How do I turn a flushable transmitter on and off? It depends on which version of the product you are using.

  • ATP-12 and FTP-8 (the new style):  Hold the button down until you see a solid yellow (ATP-12) or blue (FTP-8) LED light up, then release it.  The LED will now be flashing, and it’s ready to use.  To turn it off, hold down the button again until you see the LED go solid again, then release and it is off.  When the LED turns from its normal color to red, the transmitter is in its last hour of operation.  You may continue to use it, but when that last hour is up it will not turn on again.
  • AT-12 and FT-8 (the old ones): The little black disk in the slot is a magnet that controls the power inside the transmitter. Push it with a nail, key or screwdriver toward “ON” to turn it on, toward “OFF” to turn it off. Be sure to store it in the OFF position.

Always turn on the transmitter and receiver before the locate and confirm that they are both operating properly. Make sure you can detect the transmitter from about 12 feet away to ensure you are getting full range.

  • Find the toilet you believe is closest to the tank.
  • Flush the toilet. When the water develops a good vortex, toss in the transmitter.
  • As it leaves the building, the signal will diminish. Go outside and “home in” in the signal using the peak method. If the drain is not blocked, the transmitter will go straight to the tank.
  • Extra flushings may be needed if the tank is far from the toilet. You may need to partly fill a nearby bathtub, then empty it to get sufficient flow. If the building is locked, the transmitter can be flushed down a roof vent or exterior cleanout using a garden hose. You can also tape it to a push rod or fish tape and shove it down a cleanout or vent.

If the dig-up is to be done later, attach a fishing line or string to the eyelet so that the transmitter can be pulled back out of the line. You can also use this method to slow its voyage so the line can be traced. Or use a push rod through a cleanout, roof vent or toilet line (with toilet removed). If there is a possibility that the septic tank is made of steel (which will completely block the signal from either of these transmitters), send it down the line with the fishing line attached. If you lose signal suddenly, it’s a good sign that it’s reached a steel tank. Pull back slowly on the line until you detect the signal again. This location will be the inlet point of the tank.