Sump Pump
Sump Pump Float Switches
Level Control
The most common function of a sump pump is to protect a basement
from flooding. The pump is activated when water reaches a certain level
in the sump tank and pumps out the excess water.
The float switch is the part of the sump pump that activates the pump when water reaches a certain threshold. It is therefore an essential element to avoid flooding. The float switch is usually the first part of a sump pump to break, so it is recommended to choose a sump pump whose float switch is easily replaceable.
There are 4 types of float switches: 1) diaphragm switch, 2) vertical action float, 3) tethered float 4) Electronic “Flood Free” switch
1. Diaphragm Switch.
The
diaphragm switch is a popular type for professionals and is also the most
expensive. The entire sump pump is immersed under water and on it is a
membrane that is sensitive to water pressure. As the water level rises,
the water pressure increases and the diaphragm becomes concave, thereby
activating the switch to turn on the sump pump. When the water level drops,
the switch turns off.
Since there is no float, there is nothing to get stuck, which is a common problem with other types of sump pumps. This type of switch is not susceptible to turbulence in the tank. So if you have water entering fast, the turbulence will not trigger the switch as it might do with the types listed below.
2)
Vertical Action Float
This type of switch is recommended because it is not as expensive
as the diaphragm switch and it is superior to the tethered float. The
float is a ball that floats above the water. As the water level rises
so does the float which, at some point, will trigger the switch to turn
on the pump. This float has limited movement up and down a vertical rod
thereby giving it less freedom of movement and less of a chance to get
stuck as the tethered float does for example.
Vertical float switches are often of better quality than tethered floats and usually carry a longer warrantee.
3)
Tethered Float
The tethered float is the most common and is used for pedestal sump
pumps. The float hangs from the pump and floats on the water. As the water
rises, so does the float and the switch is triggered.
4) Electronic “Flood
Free” switch
There is a fourth type of switch that can be used. It is electric and
has no actual float. Instead, a probe wire is placed to sense the presence
of water and is activated when it becomes submerged by rising water. A
second probe wire can also be placed at a higher level to set off an alarm
switch or another backup pump. This particular switch can be used in many
types of applications.
Common problems related to the tethered float include the float accumulating grime and causing it to lose buoyancy and even sink. Another common problem is that the float gets stuck to the inner wall or pump and as a result, when the water rises in the sump tank, the float may stay submerged and fail to activate the pump.
Pedestal sump pumps have the added advantage of having the electrical unit above the water level. Other types are submerged and involve more risk of electrical accidents.
To avoid electrical shock
- Unplug the pump before putting your hands in the water.
- Use a broom stick rather than your hand to check whether or not the float is stuck.
- Use a ELCI extension cord which will turn off much like the more sensitive bathroom plugs (CFI ) to avoid electric shock. The bathroom type of plugs are too sensitive for sump pumps and are triggered too easily. A common sump pump error is to assume that a sump pump is not working when in reality it is the safety plug that has shut off. The US standard for CFI plugs is to shut off when currents reach only 5 milliamps, whereas ELCI extension cords have a higher threshold.
Mercury Poisoning
If you use a sump pump in a tank containing water that you may use
for drinking, make sure that your float switch is not made of mercury.
There are two types of tethered float switches, some are made of mercury
(which is cheaper) and others of steel. It is hard to tell the ball of
mercury apart from the ball of steel.
Electronic “Flood
Free” switch
There is a fourth type of switch that can be used. It is electric and
has no actual float. Instead, a probe wire is placed to sense the presence
of water and is activated when it becomes submerged by rising water. A
second probe wire can also be placed at a higher level to set off an alarm
switch or another backup pump. This particular switch can be used in many
types of applications.
