Your Pump Runneth Dry

You just got home and realize that you left the submersible dewatering pump running in the pit. It’s probably empty by now, and all you can envision in your mind is the shaft seizing and the motor smoking in the next hour or so.

But wait! Do not grab your truck keys and go running back to the jobsite. Relax…because you have a Tsurumi submersible pump in that pit. Tsurumi pumps are designed to handle run dry situations.


What Is Run Dry?

When a submersible pump “runs dry” it means that it has pumped all the liquid out of the pit or sump is was submersed in. The pit is now empty and the pump is still running but not pumping anything. This is what “run dry” means.

Submersible dewatering pumps are designed to be submersed in the liquid they are pumping. This is for a few reasons:

  1. Submersion helps keep the motor housing cool by transfering heat from the motor into the surrounding liquid.
  2. Submersion helps keep the lower mechanical seal cool by transfering heat from the seal to the surrounding liquid the pump is pumping.


Is Run Dry Bad?

Generally speaking, yes. Running a pump dry is not good for the pump. The motor and the lower seal must remain cool in order for the pump to continue running, which is why many submersible pumps are not engineered to run continuously. In order for a pump to run continuously, 24 hours a day, 7 days a week, it must be able to cool itself. This is more difficult than it sounds.

If a submersible pump cannot cool itself, bad things happen:

  • The motor can overheat and melt, causing catastrophic pump failure. When this happens, the motor needs to be removed and rebuilt to salvage the pump (or disposed and replaced, depending on which makes more sense). This is costly and takes time, which can badly stress a facility which relies on it’s dewatering pumps.
  • The lower seal can fail. When the lower seal becomes too hot it can warp or crack, allowing liquid to enter the oil chamber. When liquid enters the oil chamber it destroys the lubrication causing failure of the mechanical seals and seizing of the motor shaft. Liquid could also enter the motor housing, causing the motor to short out. In either case, catastrophic pump failure can result.


Can My Pump Run Dry?

Great question. What type of pump do you have? If you have a Tsurumi submersible pump, your pump can indeed run dry for extended periods of time. Let’s take a look at why this is the case.

Tsurumi submersible pumps are engineered with dual inside mechanical seals with silicon carbide faces. Silicon carbide is a very hard material which handles heat very well. The seals are housed in their own oil chamber isolated from the pumpage, which provides a clean, non-corrosive, abrasion-free lubricating environment. This prevents spring failure due to corrosion or abrasion and bottom seal failure due to loss of cooling, like what happens when a pump runs dry.

In addition to the seals and oil chamber, Tsurumi pumps are manufactured with circle thermal protectors. These devices react to excessive heat and amperage and shut the motor off so it does not overheat. When the motor returns to normal operating temperature the circle thermal protector will automatically restart the motor. This is a failsafe mechanism built into all Tsurumi submersible pumps.


The Tsurumi Advantage

Let’s get back to our scenario where you left your pump running in a dry pit overnight. Here’s how a Tsurumi submersible pump would make your life amazing:

The dual inside mechanical seals with silicone carbide faces are engineered to run continuously and do not rely on any outside liquid to keep them cool, so they are fine. No problems there. If, for some reason (be it Kona winds or the summer months) the pump motor becomes too hot, the circle thermal protector will trigger and shut the pump off to keep it from overheating. Once the motor cools down the circle thermal protector resets and the pump restarts automatically.

That’s it! It’s that simple. No need to worry about burning out your pump by accidentally leaving it running all day or overnight. This is common on busy jobsites and Tsurumi knows this, which is why they manufacture their submersible pumps with these failsafe features specifically for run dry conditions. Disaster averted.



A 2-year manufacturer’s warranty comes standard on all contractor-grade Tsurumi submersible pumps up to 1HP. This gives you extra peace of mind knowing that Tsurumi fully supports their pumps against manufacturing defects which would cause your pump to malfunction.