Water Bath

How can I make sure my boiling water bath does not run dry?

Water baths are an excellent way to maintain samples at a set temperature, though when they are run at high temperatures or for long periods of time the water will of course evaporate.

If the bath runs dry this will not only mean your samples are out of temperature, but it can also damage the bath.

There are several things you can do to ensure this does not happen.

SBB Aqua Plus water baths
The SBB Aqua Plus range of Boiling Water Baths by Grant

Keep the lid on!

It sounds simple, but making sure the lid is kept on as much as possible will reduce evaporation the most.

This doesn’t just go for long time periods when the bath is unattended – if you need to move samples in or out make sure you have everything you need to do so before taking the lid off, so it is only off for the shortest time necessary.


Choose a model with a Constant Level Device

Some water baths feature a constant level device to ensure the water is automatically topped up – particularly useful if the bath needs to be left running overnight or for long periods without monitoring.

The Grant SBB Aqua Plus range have a constant level device on the side of all units, as shown below;

SBB aqua plus bath with constant level device to stop drying out
SBB Aqua Plus model bath with the Constant Level Device shown

This is simple to set up;

“To use the constant level device, connect the inlet pipe (black) to a water supply and the outlet pipe (white) to a drain. The water level can be adjusted by loosening the lower black nut and raising or lowering the white tube. The position of the top of the tube determines the water level. Re-tighten the black nut.”


Monitor Regularly

Even baths that refill by a constant level device should be checked regularly – be sure to check the water level at least once a day, to make sure it is as expected.


Ensure there is a fail safe

Despite controls and checks in place, the bath may still dry out if these fail. Make sure that any bath you choose has a fail safe, to cut the power if the unit runs dry.

This is often referred to as “over temperature protection” and is


For more information about water baths, or other temperature control methods such as hotplates, ovens or incubators, simply follow the links above or contact us;


One thought on “How can I make sure my boiling water bath does not run dry?

  1. I really appreciate your information that some laboratory water baths have automatic sensors that help keep them topped off when they need to be running overnight. That would probably be really useful for medical labs. I wonder if they would require multiple water baths or if testing is usually done in smaller batches.

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