Deep Sampling DIS Operating Instructions

Operating Principles

The Model 425-D Deep Discrete Interval Sampler allows samples to be taken from distinct levels in a well, borehole, or surface water body, typically from submerged depths as much as 1000 m (3200 ft). Deeper applications may be possible – please contact Solinst to determine the suitability of your application. Weights are added to the Discrete Interval Sampler before lowering to overcome buoyancy at greater depths.

The Discrete Interval Sampler operates on the basic principles of hydraulics. Once the Sampler reaches the desired sampling depth, it is pressurized. The pressure acts on the top of the internal piston (large surface area) overcoming the hydrostatic pressure acting on the bottom of the piston (small surface area) pushing the Sample Release Valve open, allowing sample water to fill the Sampler body. As the Piston assembly moves to open the Sample Release Valve, it also moves the Pressure Retainer away from a small o-ring sealed opening in the bottom of the Pressure Chamber, allowing the air to vent through the Vyon Filter on the exterior of the Sampler, while the Sampler fills with water.

After the sample is collected, the pressure is released from the Sampler, causing the Piston Rod to retract, sealing the Sample Release Valve and vent hole. The sealed Sampler is then retrieved to surface, maintaining chemical stability of the sample. At surface, the sample is collected by reapplying pressure to the Discrete Interval Sampler to open the Sample Release Valve.


Sampling Pressure & Weight Requirements
No. of Weights Submerged Depth (Meters) Sampling Pressure (kPa) Submerged Depth (Feet) Sampling Pressure
psi Bar
0 50 345 160 50 3.45
0 100 345 320 50 3.45
1 200 345 640 50 3.45
2 300 520 960 75 5.17
3 400 690 1280 100 6.90
4 500 860 1600 125 8.62
5 600 1030 1920 150 10.34
6 700 1200 2250 175 12.07
9 1000 1380 3200 200 13.88


  1. A single weight has a mass of 2 kg. Add 1 weight for every 100 m (300 ft) of submerged Sampler depth, after the first 100 m (300 ft).
  2. The 1.66" OD x 2 ft Discrete Interval Sampler weighs 3.7 kg (8.2 lbs).
  3. Sampling Pressure is the pressure required to open the Sample Release Valve.
  4. The discrete Interval Sampler holds 420 mL.



Sampling with the Discrete Interval Sampler


  1. A safety support line should always be used to lower the Sampler.
  2. 425-D operates differently (in the opposite way) to our standard 425 Discrete Interval Sampler, please review instructions carefully.


  1. Before using the Discrete Interval Sampler, determine the desired submerged sampling depth.
  2. Based on the chart, determine the number of weights required for your submerged sampling depth. You may not need one.
  3. To connect the first weight, unscrew the Top Platen from the Top Retainer. Screw the weight into the Top Retainer until tight. Continue to add weights as required. Screw the Top Platen into the top of the last weight and tighten.
  4. connecting solinst 425 d deep discrete interval sampler top platen to top retainer or weight


  5. Push tubing insert into the tubing. The compression fitting nuts may have to be loosened before the tubing is inserted. Tighten the nut 1-1/4 turns past finger tight for a proper seal. Note: Be careful not to lose the two pieces of the ferrule if loosening or removing the nut from the compression fitting. Re-tightening a ferrule assembly is 1/4 turn with wrench.
  6. illustration showing tubing connection setup at top of 425 d deep discrete interval sampler


  7. Remove Sample Screen and Plug. Use a standard screwdriver to tighten the Sample Release Valve into the bottom of the Sampler until just snug. Replace Sample Screen and Plug.
  8. Using the chart, determine the correct amount of pressure to apply to the Sampler at the desired sampling depth.
  9. Turn the Pressurize/Vent Valve on the reel to Vent.
  10. Use a safety support line, such as the Model 103 Tag Line, to lower the Sampler to the proper sampling depth. (See 103 Data Sheet).
  11. Once at the desired sampling depth, turn the Pressurize/Vent Valve to Pressurize.
  12. Connect the air pump to the reel and pressurize the Discrete Interval Sampler as determined in step 6.
  13. Wait approximately 5–10 minutes for the Sampler to fill.
  14. Disconnect the air source and turn the Pressurize/Vent Valve on the reel to Vent to depressurize the line allowing the Piston to retract and close the Sample Release Valve. (ie. Sampler is still pressurized).
  15. Bring the Discrete Interval Sampler back to the surface.
  16. To retrieve the sample, remove the Sample Screen and Plug and hold the Discrete Interval Sampler upright over your sample container. Reconnect the air supply to the reel and turn the valve to Pressurize.
  17. Apply a minimum of 30 psi to open the Sample Release Valve and allow sample discharge. Increasing the pressure to 50 psi will increase sample discharge to about 250 mL/min.