Sump pumps are a good deal. They're among the least expensive home equipment, but they're highly valuable for preventing mold, mildew, and structural damage from moisture.
Water can seep up through a cracked basement floor, trickle out of leaking pipes or appliances, or flood in from clogged gutters and poor drainage. Sump pumps can help get it out.
Common Sump Pump Locations
Water intrusion will often occur at the joint between the foundation wall and its footing. It can also creep in at the windows, through tiny spaces left by ties used to hold the forms at the pouring, and any available cracks, even if they were once sealed.
Although damaged perimeter drains or a high water table may require extensive and extreme measures to correct, most problems can usually be controlled at a relatively low cost.
A very common cause of water infiltration is poor water drainage around the edge of the foundation. This can easily be prevented by sloping the ground at a rate of at least one inch per foot for a width of six feet away from the foundation.
Strategically located within the confines of your basement inside a cavity dug out of the floor, a sump pump presents a cheaper means of extracting the unwanted water outside the premises and into the graded yard.
To ease the movement of the infiltrated water toward the sump pump, the basement floor should also present you with a slight slope leading to the sump pump pit.
Sump Pump Equipment
Before buying a sump pump, you should first determine the size of the pump you really need. If you install one that's too big, as soon as the float switch triggers it on, it will empty the pit in no time at all and then stop after an extremely short cycle.
Typical pits come in sizes from 18-in x 24-in at over 25 gallons up to 24-in x 36-in at over 70-gallon capacity. One inch of water in an 18-inch diameter pit represents about 1 gallon (1.1 gal.) of water and double that for a 24-inch diameter pit.
There are usually certain periodic times of the year when the risks of flash flooding and severe storms, or melts from snow, increase the threats of flooding. Your sump pump setup should always provide enough discharge to keep all excessive infiltrations under manageable levels.
To check the rate at which the water is infiltrating an 18-in pit, run the pump until the water in the pit recedes to the shutoff level, and with the sump pump turned off, measure how far up the water will rise in one minute.
Multiply that measurement by 60, and you will get your answer in GPH (gallon per hour)—just double that result if you have a 24-in diameter pit. You should then add a safety factor by multiplying this number by 1.5 and use this as the GPH rate for your sump pump.
This should cover for all restrictions constricting the water flow, such as the static head, friction from the pipes, the check valve, and other various fittings, the sum of which forms the “friction head” of the system.
But this safety factor also covers for sudden flood surges resulting from flash storms that seem to occur from time to time, even if only on rare occasions.
Finally, as far as a pit capacity, if you get any more than 30 gallons of water in one minute, you should opt for a larger reservoir such as a 70-gallon pit.
It should also be mentioned that even though five-gallon pails are often used to serve the purpose of smaller pumps, the limited volume they can hold will cause the pump to start more often and, in the long run, result in a negative impact on the pump’s lifespan.
The Check Valve
Check valves block backflow from returning to the sump pit.
From the outlet of the pump at its base up to the point where the pipe is re-directed horizontally to expel the water outside, the already present counter-effects of the static head’s pressure against the flow from the pump can be compounded by another serious discharge which will come from the volume of water contained within the static head if you don’t have a check valve at the pump to block the backflow.
Just consider that a 1-1/4 inch diameter by 8-ft pipe to reach the basement’s vertical rise represents over 1/2 gallons of water just in the static head plus some more from the horizontal pipe that didn’t make it out of the discharge yet but still has the potential to return inside the pit.
A check valve is a device that only allows fluids to flow in one direction (uni-directional).
When a pump is activated, it automatically applies pressure behind the water to force it out through the discharge pipe and outside the building.
When that pressure is removed because the pit has emptied or the pump has stopped, gravity will take over, forcing the water remaining in the discharge pipe to flow back into the pit.
Installing a check valve at the outlet of the sump pump creates a barrier against that possible backflow of water, which instead pushes down against a spring-loaded flap inside the valve to seal it from any leaking, therefore holding the water inside the discharge pipe.
The closer the valve is to the pump, the less water will return to the pit after each cycle.
Check valves come in a variety of forms and designs to accommodate specific applications of hydraulics and pneumatics.
Since controlling water discharge doesn’t involve working with high-pressure devices, the simpler and less expensive concepts in check valve technologies are usually best suited since they’re mostly always used vertically and using gravity as an added benefit to their proper use of operation, using PVC components and rubber seals, although older models using the same basic principle with brass components instead are still in use.
Activation Switches and Other Accessories
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A vertical float switch is a very common type of switching device used to activate a sump pump.
Very common on pedestal pumps which stand about 30-in to 55-in tall, with the electric motor attached at the top and a switch mounted inside a plastic housing with a lever extending out of it over the activation rod.
The activation rod stretching from over that lever down to a few inches from the base of the pump has a large bulb at the bottom end and an adjustable stopper along its shaft.
The rod is loosely mounted onto the pump and is guided through a special bracket secured to the post of the pump. The sealed bulb is designed to float on top of the water as the level goes up and goes down.
This vertical movement causes the rod itself to also move up and down, bringing with it the adjustable stopper that will move right up to the switch’s lever, pushing up against it as the water level rises and turning on the switch, activating the pump.
As the level drops, the rod will slide back down until the top end hits the lever, flipping it down and turning the pump off. This adjustable stopper is to be properly adjusted after the pump is installed inside the sump pump pit.
This type of switch works the same as the previous vertical float switch, except that it uses a different type of switch.
The switch used here is a “reed” type switch which, in its simplest definition, consists of ferromagnetic flexible contacts inside a sealed casing and operates by applying a magnetic field next to it.
This magnetic field comes here in the form of a permanent magnet inside the float, which in turn will glide up and down a special rod equipped with reed switches, as the water level goes up and down inside the pit.
As the water fills the pit, the float bulb goes up along the rod until it reaches the top, where its magnetic field will activate the reed switch (normally open), turning on the pump.
The pump then runs until the pit is empty, and the float bulb gets at the bottom, applying its magnetic field to another reed switch (normally closed), turning off the pump.
A tether float switch is basically a switch assembly mounted inside a floating bulb attached to a cord that is tethered to the pump itself.
As the water level rises, the bulb will float and swing out as it tilts over its side held by the cord, and at a certain level, the switch assembly flips over, causing the switch to turn on and start the pump.
The pump then empties the pit causing the float to drop down with the water level until it reaches the bottom, where the switch assembly flips over and turns the pump off.
The swinging motion of the float tethered to the pump causes it to be impractical in smaller pits as this can cause the float to be impaired by floating debris and by the pit wall.
Although it is a more popular choice, this is a definite drawback along with the fact that it is subject to suffer from wear due to the constant movement on the tether and requires tether replacement every three years.
If you have two electrical cords coming from the sump pit, it is likely equipped with a piggy-back plug, also called a “switch plug.”
The tether cord with the plug, which has male prongs on one side and a female receptacle on the other side, has the hot male prong feeding into one side of the float switch at the end of the tether, and the other side of the float switch returning through the neutral line to the plug where it is hooked up to the hot female receptacle to deliver the hot voltage to the motor through the pump’s plugged-in cord.
The neutral wire from the pump’s cable then provides the return path through the neutral prong of the pump’s plug, through the neutral side of the piggy-back to finally return to the circuit’s neutral through the wall outlet, just waiting for the float switch to be activated from the movement of the water and power up the pump.
This type of hookup presents you with a real asset when checking out the pump motor, as it lets you remove the switch out of the circuit.
This type of switch is probably the most reliable one to have installed since it doesn’t have any moving parts that can fail over time.
You should make sure, however, that it complies with the amp rating of your pump.
Otherwise, the electronic sump pump switch is basically a piggy-back switch, and if your pump came with a piggy-back tether or another type of switch plug, it can simply be removed and replaced with an electronic piggy-back switch.
The control module of the switch plugs in the same way as any piggy-back plug with male prongs on one side and a female plug on the back of it where the pump is to be plugged in and goes plugged into the same regular outlet in place of the old switch plug.
It comes with two sensor probes wired to the module, one to detect the high water level and the other for the low water level.
The high-level sensor goes secured to the discharge pipe with a tie wrap where you want the pump to start the cycle, and the low-level sensor is at the height where the pit is empty, and the cycle needs to stop the pump.
As mentioned above, they’re ready to replace any other type of piggy-back switch.
If however, your pump’s float switch is wired into the pump, you just need to lift the float in a position that closes the float switch and secure it permanently in that position (with tie wraps) so that it stays on.
You can then install both sensors along the discharge pipe as described above and plug your pump into the electronic module to have your setup ready to go.
If you’re planning to get an electronic sump pump switch, it might be a good idea to look for one also equipped with a high liquid level alarm.
Those alarms are also sold separately but might be cumbersome to install if the pit is not large enough to accommodate a second tether float, as most of them use. Those are designed to send a high decibel sound warning when a water infiltration occurs.
If purchased separately, however, you’ll find that there is a great price variance with different models, running anywhere between $25 to up to $700. So you could probably be the wiser by evaluating the online reviews describing all the pros and cons of the popular models before settling for any specific model.
How to Prepare for a Flood
Preventing Basement Flooding During a Storm
Sump Pump Backup Systems Explained
5 Sump Pump Well Maintenance Tips
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