"Low Tank Water" switch ?

[schmism]

Float switches are rather clumsy and can get hung up or fail in repeated use.

I suppose that depends on the quality of the switch. As every municipal facility that has sewage lift station relays on a series of float switches. If they are good enough for commercial 100% duty sewage lift stations .... why reinvent the wheel. aka KISS

 

[aczlan]

I suppose that depends on the quality of the switch. As every municipal facility that has sewage lift station relays on a series of float switches. If they are good enough for commercial 100% duty sewage lift stations .... why reinvent the wheel. aka KISS

Ayep. We have (knock on wood) never had an issue with the float switches in the pit at the hotel. We have had a lightening strike take out one leg of the 220 circuit that the pumps run on, we have had junk jam up the grinders and we have had a pipe break and allow the slurry to backfeed into the tank instead of going out.
But (knock on wood) in the 5 (almost 6) years that they have been in operation we have never had an issue with the float switches.

Aaron Z

 

[Raspy]

With sludge systems you pretty much have to have a float of some kind because of the conductivity and foreign material in the mix. Whatever works is fine.

I've had the "bulb on the end of a cord" system fail by getting hung up on things in the tank, the "sliding float" get stuck and fail, and the floating PVC tube that operates an out-of-the-tank switch, let in contaminates and become covered with growth to where they become stuck. I've also had a number of float systems fail because of turbulence over time that wore them out. All of these required a hole in the tank somewhere and I try to keep that to a minimum. No bugs or dust in, no friction with movement through the hole and no electrical cords passing through a tank wall. Also, the slider or bulb systems have a pre-determined differential between off and on. This works for sumps, but not so well for tank filling. But, again, whatever works in your case is fine. I consider a sludge system to have far different needs than a fresh drinking water system. Hot tanks and insulated fiberglass tanks are even harder to make work well. And, for me, the system needs some kind of warning system, if it's not working right, to protect the pump. This can be a system that shuts off the pressure pump, or turns on a light, or something. The one I'm working on now will simply run the pressure pump until it burns up if the tank runs out of water. That has to be fixed.

Either way, the cooler, cleaner and less turbulent the better. If it only gets very occasional use, like a sump pump, it should have a way to get exercised occasionally. I just found one the other day that runs fine but won't pump because of a stuck and dry check valve. It's a flood waiting to happen.

 

[Egon]

And is there a pair of switches in an assembly for both the "on" and "off" levels ? Or do you just kludge something together once you have the switches ?

Bob, you have a plethora of switches to choose from. It comes down to your level of expertise, availability of instruments and money available. The type of tank and access points is also to be considered.

The float switch may be the simplest. By using two you can start and stop for low and high levels.

Then would come the electrical probe type. These are usually installed on the side of a tank on a nozzle.

Another would be a pressure sensitive switch installed at the bottom of the tank. they will come in a version that has stop/start capability and again may require a nozzle at the bottom of the tank.

There are lots more as a Google search would show.

And don't even think of ultra sonic.

Consider checking in with your local farm supply store or electrician for specifics on what seems to work for them.

 

[tommu56]

some thing like this

GE 2900B3S1C1-20 Open Tank Float Switch note this one closes on rise (wrong type for filling tank)

You can adjust the weight position and the length of the cable to turn on and off minimum is about 9" of travel.

another choice

http://www.grainger.com/Grainger/SJERHOMBUS-Float-Switch-3HCV1?Pid=search

Float Switch, Mechanical, Tether, Normally Closed, Max. Amps Running 15, Voltage 120/230, Cord Length 30 Ft., Wire Gauge 14, Pumping Range Min./Max. 7 to 36, Tether Length Min.-Max. 3 1/2 to 24 In., Float Length 3 9/16 In., Float Dia. 3 3/64 In., Max. Temp. 140 F, Max. Temp. 60 C, Float Material PVC, Includes Mounting Clamp Assembly
Grainger Item #3HCV1

you need it to closed in the down position open when it floats up
tom

 

[pat32rf]

A float switch is definitely your easiest way. They do come with contacts to start on drop but they might be hard to find. There will also be no "diferential" (high-low level) adjustment. A boiler "high voltage" probe arraingement is more adjustable as you just put a probe at the high and low points. Easier than it sounds. Ask about a boiler condensate pump switch....

 

[grsthegreat]

float switches work fine. mines been working 100% for 14 years (hope this post doesnt jinx it).
If your worried they have piggyback switches.... meanine 2 floats that do the same ting. if one fails the other kicks in.

Or you can install an alarm float that rings alarm if level gets too hogh or low.

you can find any of these switches at wholesale plumbing and/or well drilling shops. there not too expensive.

Heck, our Home Depot used to carry them till a few years ago.

 

[mmurphy]

The next question is, is this temporary set up or a permanent? If it is a temporary, I would go with a plain simple float. The pedastal type sump pumps worked on this easy set up for many years. I have been in water plants that use it also. A stilling well for the float will keep float running consistant up and down. A stilling well can be made simple as a PVC pipe anchored in place with an opening at bottom that allows water to slowly enter.