# solid-state water overflow detection



## RustyShackleford (May 23, 2016)

My septic tank overflowed onto my lawn the other day.   Noticed funny smell, saw standing water near tank, it smelled like poo, and called septic man.  He pumped tank and determined my toilets were both leaking through flapper valves (I didn't realize that could be happening without hearing weird noises at night, but it was).   He reckoned new flapper valves would solve problem, and hopefully it has, but I'm a little spooked at talk that the overflow could wash solids into the leach field and damage it.  So I want some detection that fluid level in tank is getting too high.

You can buy overflow detectors, but they involve mechanical float valves (like the one in a toilet tank).  These are binary (overflow, or no overflow) and they seem clumsy - you have to install them at the right height, etc - and likely prone to failure.   Seems to me that a better and easier-to-install one could be solid-state.  Just a rod that you insert through a hole drilled into the tank hatch, with several electrodes in it, each of which detects fluid has reached its height.  I'm thinking it could just be a 2-3ft piece of PVC that covers the full vertical height of fluid levels I'd want to detect.  One long electrode that full height, and several point electrodes nearby.   N+1 wires coming out, where N is number of point electrodes, all connected to simple N-channel A/D converter which measures resistance between long electrode and each point electrode.   Presumably the resistance between long electrode and a point electrode above water level would be orders of magnitude higher than resistance to electrode submerged in poo-water.   

Anyhow, this probably seems way too complex too many.  But I'm a EE and it sounds like fun to me, so I welcome suggestions from any like-minded people !


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## RustyShackleford (May 23, 2016)

This looks most interesting:

https://www.parallax.com/sites/defa...pe-Standard-Liquid-Level-Sensor-Datasheet.pdf

I just wonder how a liquid that includes a bunch of funky solids is going to affect any measuring device.


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## velvetfoot (May 24, 2016)

How about something like this:
http://www.flologic.com/flologic-guide/FloLogic-System-3.5-Cut-Sheet-7-2015.pdf


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## peakbagger (May 24, 2016)

Take a look at Hamilton Marine for bilge float switches. A septic tank is very aggressive atmosphere and the hydrogen sulfide will corrode anything except for encapsulated wiring and components. Generally you want to wire it up so that the circuit is Normally Closed so that loss of signal fires off the alarm. That usually will pick up if the wires or switch fails.


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## semipro (May 24, 2016)

Could you install your sensor in an underground vault near the tank such that when the soil starts to get saturated water rises within the vault and triggers your alarm?
The "vault" could be something as simple as a perforated PVC pipe installed a foot or two into the soil with a cap on top.

I appreciate all too well the need to get geeky with the electronics but a simple magnetic reed float switch like the condensate switch below would be pretty foolproof and cheap.





BTW: I too was concerned about solids (mainly lint) clogging my drain field so I installed an outlet filter.  I'd like to have some indicator of high water to let me know the filter is clogged.   Your project interests me.


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## sportbikerider78 (May 24, 2016)

Warrick controls is a division of Gems Sensors and Controls.  I used to work there as a manufacturing engineer and manager...this is exactly what you are looking for.  Talk to a sales engineer and they will sell you the right system.

This is not cheap.  But if you want an engineered solution that will work, they can hook you up.

http://www.gemssensors.com/Level/Warrick


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## RustyShackleford (May 24, 2016)

velvetfoot said:


> How about something like this:
> http://www.flologic.com/flologic-guide/FloLogic-System-3.5-Cut-Sheet-7-2015.pdf


Sort of a "supply side" solution.   Not a bad idea, but I think I want to monitor the septic tank level directly.


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## velvetfoot (May 24, 2016)

RustyShackleford said:


> I think I want to monitor the septic tank level directly.


But why, if the source of the water you are concerned with is the well?  This solution could also shut things down when out of the house or certain other criteria are met, potentially saving you a lot of money in house repairs.


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## RustyShackleford (May 24, 2016)

velvetfoot said:


> But why, if the source of the water you are concerned with is the well?  This solution could also shut things down when out of the house or certain other criteria are met, potentially saving you a lot of money in house repairs.


Good point.   But the septic tank could also overflow with normal water usage, if the leach field is not working up to snuff.


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## blades (May 24, 2016)

Pvc pipe and and a pvc pipe smaller enclosed to act as float Magnet on top Extends out side tank But   still inside first pipe ( will need small air vent perhaps, series of ss mag sensor switches for various levels ( not a fan of reed switches as they tend to stick and flake out over the long haul) can be simple or as complex as you want.  But any of this is just reinventing the wheel.

Just a thought maybe you could get hold of the sepic guy on the red/green show.


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## Highbeam (May 24, 2016)

The actual commercial solution is a float switch. They are used all the time in pump tanks for septic effluent pressure distribution systems. If the pump or the regular on/off floats fail to activate the pump then as the liquid level rises the "alarm" float activates the alarm alerting you that something isn't right. Off the shelf stuff.

A leaking toilet allegedly caused more water to flow into your tank than normal. Every drop into the tank is supposed to cause a drop of effluent to leave. Your drainfield works by absorbing water NOT evaporation. It has a gpm capacity that was exceeded so it backed up which prevented effluent from leaving the tank which means the level went up and over. If you had infinite drainfield capacity then the tank level would never have risen. Normally you see surfacing effluent above the drainfield before you get an overflow at the tank since the tank is normally sealed up pretty tight and the ground is lower over the drainfield.

The failure you experienced would not wash solids into your drainfield. The septic tank has layers, sludge on bottom, scum floating on top, and the "clear zone in the middle which is where the outlet picks up effluent for discharge. Extra clean water coming in would pass through the clear zone and go out. There are no solids in that extra water that need time to sink or float into the scum or sludge.

Effluent filters are good. Synthetic lint doesn't sink or float properly and does not degrade in your tank or in the drainfield. It will plug your drainfield over time.

What I do, rather than add electronics to a gravity system, is add a cleanout between the house and the tank and leave the cap loose. This will prevent backups into the home (big bucks). Most of the plugs I've cleared over the years are at the inlet to the septic tank from some dang kid flushing too much TP.


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## Highbeam (May 24, 2016)

I would expect you to hear the toilet tank refill if the flapper was leaky. It would happen in spurts 24 hours a day.


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## RustyShackleford (May 25, 2016)

Highbeam said:


> I would expect you to hear the toilet tank refill if the flapper was leaky. It would happen in spurts 24 hours a day.


I would've expected it too.  I was very taken by surprise when the septic man showed me the continuous flow into the tank (after letting the drain pipes empty out after flushing).


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## semipro (May 25, 2016)

You can put a little food coloring in your toilet tank to see if you flapper valve is leaking.


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## Ella Rollins (Aug 5, 2016)

I came across the same situation and I got my toilet repaired by plumber few months ago. They recommended me to use Waterline Water Alarm 9VDC 6’ sensor. It really works. This sensor does not need any installation. I’ll just place it near the water source and it will detect as little as 1/32” of water. Incase of any overflow this sensor gives that 110db alarm that can be heard throughout the house.


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## velvetfoot (Aug 6, 2016)

No, this is an internal leak.  That being said, the ones I got from Home Depot are cheap, and one went off the other day when condensation dripped down from the toilet because it was a humid week.


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## Ashful (Aug 6, 2016)

An aside to your actual question, but I'd be replacing the toilet inlet valves, along with the flappers.

1.  They could be leaking into the refill tube rather than thru flapper, which is more likely if you're not hearing them cycle.

2.  A good inlet valve should have some hysteresis, meaning it will hold then cycle on a leaky flapper situation, not just silently bleed all day and night.


Sent from my iPhone using Tapatalk


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## RustyShackleford (Aug 8, 2016)

> You can put a little food coloring in your toilet tank to see if you flapper valve is leaking.


Yeah, did that after I replaced the flappers, and all looks good.



> An aside to your actual question, but I'd be replacing the toilet inlet valves, along with the flappers.
> 
> 1.  They could be leaking into the refill tube rather than thru flapper, which is more likely if you're not hearing them cycle.


So if my flapper valves are good (which I believe they are, having replaced them and done the food-coloring test), would a leaky inlet valve be dumping water down the drain without me seeing the food coloring in the toilet bowl ?


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## Highbeam (Aug 8, 2016)

RustyShackleford said:


> So if my flapper valves are good (which I believe they are, having replaced them and done the food-coloring test), would a leaky inlet valve be dumping water down the drain without me seeing the food coloring in the toilet bowl ?



The leak would fill your tank until it overflows through the standpipe in the tank. I believe that this pipe dumps into the bowl.


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## RustyShackleford (Aug 8, 2016)

Highbeam said:


> The leak would fill your tank until it overflows through the standpipe in the tank. I believe that this pipe dumps into the bowl.


Oh yeah, I checked, that's definitely not happening.   And you're saying even if it were, I'd se the food coloring I put into the tank bleed into the bowl.   Thanks.


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## Highbeam (Aug 8, 2016)

RustyShackleford said:


> Oh yeah, I checked, that's definitely not happening.   And you're saying even if it were, I'd se the food coloring I put into the tank bleed into the bowl.   Thanks.



Try dripping the food coloring right down the overflow tube to see for yourself.


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