One of the most requested features for this application is user-alerts for detected problems. I'm happy to report that this feature is now available. It took a little time to implement because I wanted to avoid a spam-like experience. Specifically I wanted to make sure (1) that you can turn on and off alerts as you please, and (2) that you can limit how often you are alerted about a problem. When you log in to the web site to check your system you will now see a link labeled "Alert Settings". Following the link will display this screen:






For each of the "system checks" performed on your system each day, you can choose (1) not to email any alert, (2) to email an alert just one time (when the problem first occurs) or (3) to email daily, while the problem persists.

The email address to which the message is sent is the same as the one you use to log into the system.

I'd be interested to hear what you think: Is the message informative? Would it be valuable to allow alternate email addresses or sending text messages to your cell phone? All these variations are possible.

Though I haven't done much technical development since early this year, the nine installed septic system monitors are all working well, collecting and analyzing the activity of their owners' systems. Reviewing the data that is being collected I noticed something unexpected and pretty cool: When the septic pumps turn on, the amount of time they stay on is very consistent. I added a new charting option to the web site to show this fact. First, here is the 'classic' chart seen on the web site: It shows the cumulative time a septic pump has run in terms of "minutes per day", in this case broken down weekly:





As you can see, this system goes on from as little as 1m:15s per day up to nearly 3m per day. Now consider how long the pump turns on each time it does so:


This pump always runs for about 2m:20s. It's extremely consistent! The yellow bars show the median run time, and the dark error bars delimit the inter-quartile range (the range of values within which half the run times lie). This is just a statistically fancy way of saying that the pump is extremely consistent in its run time.

What does this mean and why is it cool? We have to consider what affects the cumulative time (the first chart above) and the run time (the second chart above). The cumulative time reflects how much you use your septic system. If you go on vacation it drops to zero. If relatives stay for the holidays and bathe a lot, the cumulative time will spike up.

However the pump run time is insensitive to all of that. The pump is switched on and off by a float switch down in the pump tank. The diagram at the top of this page shows the idea

http://www.plumbingsupply.com/alarm.html

(though the specifics of your system may differ). The run time is how long it takes for the pump to lower the water level from the 'on' position to the 'off' position, and this only depends on (1) how strong the pump is and (2) how much resistance it encounters. Since the run time is so consistent, we should be able to detect the beginnings of mechanical failure in the pump and/or minute changes in downstream resistance due to a developing clog.

And that, to me, is pretty cool.

Why is a Septic System Monitor Useful?

It seems generally true that you don’t need to know how something in your home works until it stops working. A few months after we moved into our house in 2006, Jenine and I started learning about our septic system. An alarm went off in our garage in the middle of the night. Over the next day or so we learned that our septic system has two pumps for moving liquid from one part of the system to another, and one of them had stopped working. The alarm indicating that a “pump tank” was nearly full. Replacing the broken pump cost over $1000. 13 months later (just after the warranty expired) the pump failed again, necessitating another four-figure investment in our home. We haven’t had any problem in the subsequent 2 ½ years, but that second failure left a lot of unanswered questions: Was the pump “burning out” for some reason? Could ground water have been getting in to the system, causing the pump to run excessively? Could the pump have been “stuck on” somehow? Was the pump pushing against a downstream clog? The experience basically left us wanting to know what the heck is going on down there. I started looking around for some device that would track and report on the septic system activity. The closest thing I could find is a run-time meter, which just tells you how many hours a device has been on in its life time. What I really wanted was a device that would give a daily summary so I could see the baseline activity, any seasonal trends (more activity in the Fall/Winter might mean a ground water leak) and any sudden change (the pump suddenly stopping altogether or suddenly going on a lot, the latter meaning that a switch is stuck on or that the pump is pushing against a clog).

Not finding a suitable device for sale, I ended up making my own, using an old Palm Pilot and a few miscellaneous electronic bits. The monitor has run for over two years, showing that the pump tank pump runs for an average of about four minutes/day.

More recently I decided that it would be more convenient to have a web-based version of the monitor, so that the activity could be seen on any computer, rather than just on the little Palm Pilot screen in our garage. I found a low cost way to connect a sensor to the internet and set up a web-based program to display the data. You can see our septic system activity by looking at the "live demo" at:

http://omwatcher.appspot.com/

It shows the activity of both pumps in our system. You can also see where we went out of town in June (no activity). The sand filter pump sensor was added on June 6, which is why there aren’t any bars before that. The system also has a number of 'checks' that it runs daily, to see if it's broken or if the monitored pump(s) are on too much or not enough.

The program can track and display the activity for any number of households, having any number of sensors each. Moreover, the wireless technology makes it possible to add more sensors and/or households to the existing so-called Home Area Network (HAN), limited only by the range of the wireless devices. Our next door neighbors have just one pump in their septic system, and are now tracking it using the same web-based program.

I'd like to add more households to this system. I understand that there are "operation and maintenance" professionals who contract with homeowners to maintain their septic systems. My thought it that this tool could enhance such a service, a trained professional being the best one to monitor and interpret the run information.