Point Source Bailer for discrete interval groundwater sampling

Solinst 429 Point Source Bailer

  • Simple and Cost Effective No expensive ancillary equipment is needed
  • Range of Lengths and Diameters 0.5, 1, 1.5 and 2 inch diameters and standard lengths of 2, 3 and 4 ft available
  • Ideal for aquifer profiling
  • Stainless Steel Construction
Product Options


Point-source sampling collects water as it flows into the desired sampling point, which prevents purging and the disposal of purged water. Because of this, point-source sampling is perfect for obtaining high-quality groundwater samples from specific depths.

Often used to profile open boreholes and screened wells, the 429 Point Source Bailer collects samples from specific levels and inflow points. The mixing of water from different levels is prevented reducing sample contamination to minimal levels. Ancillary equipment is not required, making point-source sampling in hard-to-access locations more manageable. With a diameter of only 0.5” (12.7 mm), the miniature model is suitable for direct-push devices and narrow tubes.

Method of Operation

While the bailer is slowly lowered on a support line to the depth of the desired source, both ball valves open, allowing water to flow through the sampler. Once the desired sample depth is reached, the bailer is raised in a steady, controlled manner. The upward momentum and water weight keep the ball valves closed, and the ball valve located on the top of the bailer prevents the sample from mixing with water in higher levels. The bottom valve prevents the sample from leaking out of the bailer. When the bailer reaches the surface, the top vent is opened allowing sample material to drain into a container. Before taking another sample the bailer should be decontaminated.

The 429 Point Source Bailer consists of well-built components made from high-quality materials, including 316 stainless steel with PTFE/FEP ball valves and Viton O-rings. The sampler is supplied with a sample-release device made from stainless steel. This minimises the loss of materials that can occur during the transfer between the bailer and the sample container.

For use with the 429 Point Source Bailer, the Solinst Model 103 Tag Line is recommended. It's mounted on an easy-to-use reel, and includes marks at either 1 ft or 5 ft intervals (0.5 m or 1 m).

Manufactured by: Solinst
Model: Solinst 429 Point Source Bailer

Services offered for this product

  • Sales
  • Rental
  • Installation
  • Calibration
  • Maintenance


Borehole profiling
Well monitoring
Point sampling


Bailer Capacity (per 2 ft. length)
O.D. inch Capacity oz O.D. mm Capacity ml
0.5 1.712.750
1.0 6.525.4190
1.5 1638.1430
2.0 2950.8860
Point Source Bailers come in standard lengths of 2ft. (610 mm), 3 ft. (910 mm), or 4 ft. (1220 mm)


Related products


A device that collects water samples at a specified depth without need for purging beforehand. Samples taken reflect only the specific water chemistry at the time and location where the sample was taken. It can also be referred to as an individual or catch sample. This type of sampling is recommended when standard purge sampling is impractical or not efficient. Groundwater sampling relies on the principle that groundwater is characteristic of the water outside the well at that depth.
Three different modifications of the grab samplers are offered by Solinst: the model 428 BioBailer which is single use and made of biodegradable PVC, the Model 429 Point-source Bailer which is reusable and made of stainless steel, and the Model 425 Discrete Interval sampler which is essentially a pressurised bailer. They are all modifications of the basic bailer.
The 428 BioBailer and 429 Point Source Bailer require a suspension line for raising and lowering the bailer. It is recommended you use a Solinst 103 tag line- this can be attached to the bracket at the top of the sampler. A sample release device is included with each bailer, and discrete interval sampler, to help with transfer to a sample bottle. The 425 Discrete Interval Sampler includes tubing, of a specified length, that is attached to the sampler for raising, lowering and pressurising the sampler. The tubing is on a reel with fittings to allow the sampler to be pressurised using a high-pressure hand-pump.
The Discrete Interval Sampler is the only sampler that collects a representative a sample of a particular depth without interference from other levels. This is because the sampler is pressure sealed for transport up and down through the water. In the 428/429 bailers, water passes through the body so this is not the case. The 429 has check balls at both ends of the bailer, so as the bailer is lowered, water flows through it until it reaches the required depth. But upon return to the surface the check balls are closed to prevent the water from mixing. However, if the check balls become dislodged there is still a risk of mixing. The 428 has one check ball at the bottom, therefore there is more risk of the sample mixing with water above. These bailers are not truly discrete as the samples from them can only be considered representative of a particular depth when used optimally. The check balls provide a good seal but it is not completely leak free. So if the models 428/429 are used past their maximum recommended depth, potentially the samples can be lost, if they are raised long distances above the water surface to the ground surface. Samples collected provide a snapshot of the water chemistry at a specific point in the well at that moment in time only. A more representative/average sample can be attained using sampling pumps that purge and then sample, drawing water from a larger area over a longer period of time.
Samplers should be slowly and gently lowered through the water column, to create as little mixing as possible, and the sample collected for the desired depth is representative of that depth. And in the case of the 428/429 bailers they should also be gently raised to avoid the check balls being dislodged and the sample contaminated. For all samplers it is recommended a sample release device is used.