The RAD AQUA is an accessory for the DURRIDGE RAD7 scientific radon detector that enables the continuous monitoring of radon in water such as groundwater, lakes, rivers, and other aquifers. It is used to bring the radon concentration in a closed air loop into equilibrium with the radon concentration in a flow-through water supply. The RAD AQUA consists of a spray chamber, called an “exchanger”, that brings the air and water into equilibrium. The radon in the air is monitored continuously by the RAD7.

The partition coefficient (the ratio of radon concentration in the water to that in the air at equilibrium) is determined by the temperature at the air/water interface. This temperature is measured with a temperature probe inserted into the exchanger. At typical room temperature the coefficient is about 0.25. That means the concentration of radon in the air is four times higher than in the water. As a result, the system’s sensitivity to radon in water is four times higher than the sensitivity to radon in air.

It takes time for the water to deliver radon to the air loop and for the RAD7 to respond to the changed radon concentration. With optimum configuration the response time of the system may be reduced to less than half an hour.

Product highlights
  • Radon and Thoron Measurement: Continuous monitoring in water.
  • Simple to Use: Just connect it to the tap and hook it up to the RAD7.
  • Fast: 95% response in 30 minutes.
  • Sensitive: Can monitor radon even in concentrations below 1 pCi/L.
  • Accurate: Measurements are precise within +/- 5%.
  • Clean and Safe: Involves no hazardous materials or chemicals.
  • Complete: Includes temperature logger and necessary software.
  • Great Value: Practically no running costs.
How it works

Water passes continuously through the RAD AQUA exchanger. Air flows in a closed loop through the exchanger and through the RAD7. Radon in the air comes into equilibrium with radon in the water. From the radon concentration in the air and the temperature of the air/water interface, the radon concentration in the water is determined. This is the fastest, most sensitive method of measuring radon in water, and it can monitor both radon and thoron levels continuously.

The RAD AQUA is capable of delivering 0.19 gpm, 1.14 gpm and 4 gpm, respectively, at 20 psi water pressure.

Testing hot spring waters with the RAD AQUA in Yellowstone National Park. Photo by Ian Cook.

RAD AQUA Physical Specifications
RAD AQUA Shipping Dimensions 16″ x 8″ x 8″ (41 cm x 20 cm x 20 cm)
RAD AQUA Shipping Weight 7 pounds (3.2 kg)
Purchase the RAD AQUA

Complete RAD AQUA
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The RAD AQUA comes complete with:

  • Omega Temperature Probe
  • Omega OM-EL-USB-TC Temperature Logger
  • Three pairs of spray nozzles (WL1/4, WL1 and WL4)
  • Roll of Teflon Tape

The following replacement parts are also available:

Omega Temperature Probe

$115.00Add to cart

Omega OM-EL-USB-TC Temperature Logger

$225.00Add to cart


RAD AQUA Assembly


RAD AQUA Standard Configuration Diagram
RAD AQUA Standard Configuration Diagram

RAD AQUA Configuration Diagram (with DRYSTIK and Water Switch)
RAD AQUA Configuration Diagram (with DRYSTIK and Water Switch)

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