It’s sump pump season again and in addition to reminding our customers that it is time to do some seasonal checks, it’s time to share some information about the brain of many pump systems, including sump pump systems. If the pump is the heart of a water system, then the float switch is the “brain” of the system. Most of our customers have pumps that need to be turned on or off automatically. Some common applications for this are:

• Sump pumps that empty basement drains

• Submersible well pumps that fill large storage tanks

• Pumps in septic tanks that pump out to septic fields

In this article, we are going to discuss what type of float switch is needed for each of these applications and even show you some of the parts and pieces that are involved in making this happen. If you have problems with your water tank or sump basin overflowing or you have a problem with not enough water in your tank, then keep reading because the proper operation of your float switch could be the cause of your problem.

Pump Up Float Switches (otherwise known as a Normally Closed float switch) are used when a pump is being used to fill a storage tank. The pump up float switch is installed near the top of the storage tank and as the level in the storage tank increases the float switch will raise and the switch inside of the float switch will open causing the pump filling the tank to turn off. In this application the power for the pump is first routed to the float switch in the top of the tank and then to the pump that fills the storage tank.

Pump Down Float Switches (otherwise known as a Normally Open float switches) are used when a pump is emptying a drain or a tank and you want the pump to shut off before it completely runs out of water and starts sucking air. Sucking air can cause the pump to loose prime, become air locked, waste electricity and shorten the life of the pump. These float switches, in most cases, are placed 4-6” above the pump suction. When the water level increases the switch in the float switch closes and power is supplied to the pump. The pump then turns on and removes the water from the sump or tank. As the water level drops the switch inside the float switch falls down, the internal switch will open and the pump will turn off.

Float switches must always be secured properly in the tank with high quality all plastic zip ties to a secure part of the tank or pump or by using a float weight to ensure that the float is held at and pivots and the correct height. One of the biggest problems we encounter with float switches is that they are not tethered properly, they come loose or they get tangled up in tight places or with the very pump they were installed to control. This can result in pumps not turning on or off when they should. Make certain all wiring is properly and neatly secured and you’ll save yourself a headache!

How to choose the right float switch

There are several considerations when selecting a float switch beyond knowing if you want a pump up (normally closed, NC) or pump down (normally open, NO) pump switch. These consideration are:

• Pumps Size. If you choose a float switch rated to run a 1/2 Horsepower pump and run a 1 or 2 Horsepower pump, then that float switch will probably not last very long and you will get frustrated when it lasts only a few months. Pumps with higher horsepower ratings need a float switch with an internal switch capable of handling the higher power flowing through the circuit. To find out what size float switch you need, look at the amperage/hp rating of your pump!

• Pump Connector. If you want a float switch that can simply plug into a normal power outlet you need to choose the correct style of piggyback float switch that will allow you to plug the float switch into the wall and then plug the pump into the back connector on the float switch. Keep in mind that different voltages and countries will have different style connectors, so please verify that the connector is the same style as your pump before purchasing.

• Cord Length. You don’t want to deal with splices in float switches in wet environments as this is a serious electrical safety issue! Make sure you get a float switch with a long enough cord!

• Wide or Narrow angle float switch. There are many, many float switches on the market and quite a few of them are not suited for use in controlling a pump! Why? Because they are narrow angle float switches and you need high quality, wide angle float switches that are designed to last for many years. The problem with narrow angle float switches is that only small changes in water level will cause the pump to turn off or on, even ripples in the water or splashed from water coming into the tank or sump. Turning the pump off and on rapidly and repeatedly is a great way to generate excess heat in the pump’s motor and permanently damage the pump or drastically reduce its operating life! A wide angle float switch means that the water level needs to change by several inches to cause the float switch to either turn on or off.

• Type/Quality of Liquid. If the float switch will be used in Potable water, it should be rated for this use! If the liquid is hot, make sure you get a float switch rated for the correct temperature!

At Oakville Pump Service we only use the highest quality float switches available! To help you decipher which one you need for your application here is a sample list with descriptions! These part numbers below are for wide angle SJE Rhombus Float Switches that our crew commonly use. In fact, our service technicians typically carry these on their trucks as a standard item!

20PMPD1WP 20’ Cord, Pump Down (Normally Open) Float Switch with 120 Volt Piggy Back Plug 15 Amps maximum. Potable Water (can also be used for sumps)

20PMPDWOP 20’ Cord, Pump Down (Normally Open) Float Switch 120/240 volt operation no plug provided 15 Amps maximum. Potable Water (can also be used for sumps)

20PMPUWOP 20’ Cord, Pump Up (Normally Closed) Float Switch 120/240 volt operation, no plug provided, 13 Amps maximum. Potable Water (can also be used for sumps)

15PMWPSWE 15’ Cord, Pump Up/Pump Down float switch 120/240 volt operation, no plug provided, 15 amps maximum. Potable Water (can also be used for sumps). Many pumps have a relay/contactor that turns the pump on or off and a float switch is used to control the relay. This type of float switch is frequently used with pumps that have contactors/relays that control the pump as it can be configured to operate as either a pump up or pump down float switch, but pay attention to the installation instructions!

Do I need a float switch or sensor in my well?

Before we wrap up, there is one last of application that we will discuss, not because it requires a float switch, but rather because it DOES NOT require a float switch! Many people want a float switch to install in their well to turn their pump off if it runs out of water. Pumptec and Pumpsaver both make controllers that are designed for this application. These are very intelligent devices that know when your pump is running out of water, turn it off, and then will turn it back on after an appropriate time for the water level in your well to recover. This means you don’t need to try to install sensors in your well where they can get tangled up or fouled with minerals or corrosion. Keep in mind that these controllers only sense when your pump has run out of water and turn it off, they aren’t designed to shut your pump off when your tank is full, so you’ll need a float switch for that! These devices will also protect your pump from low/high voltages as well as rapid cycling if there is a problem with your pressure tank or pressure switch.

A word of CAUTION is in order. Working with float switches means that you are working in proximity to both water and electricity, often at height or in confined spaces. Please familiarize yourself with and follow all applicable safety measures and electrical/building codes when installing and connecting a float switch!

If you want to ensure you get the right float switch for your application and have it installed properly, make sure the crew at Oakville Pump Service is on your team. We keep the water flowing for many of our customers in the Napa Valley!