A bladder pump uses compressed air or nitrogen to push groundwater to the surface through a flexible internal bladder, without the water ever touching the compressed gas — making it the standard EPA- and ASTM-compliant tool for low-flow VOC and PFAS groundwater sampling. This guide compares Solinst bladder pump models, controllers, and how they stack up against peristaltic and submersible pumps.
What Is a Bladder Pump and How Does It Work?
A bladder pump is a submersible, gas-operated sampling device: hydrostatic pressure fills a flexible internal bladder with formation water, then a surface controller sends compressed air or nitrogen down a drive line to squeeze the bladder and push that water up a separate discharge line to the surface. Because the compressed gas never contacts the water sample, bladder pumps avoid the gas-stripping and aeration bias that rules out suction-lift pumps for volatile analytes.
This is why the EPA's Low-Flow (Minimal Drawdown) Ground-Water Sampling Procedures and ASTM D6771 — the same standards referenced across ERE's low-flow sampling guides — name bladder pumps as a preferred device for VOC-sensitive and PFAS-sensitive monitoring programs, alongside dedicated submersible pumps.
Fill and discharge cycle
- Fill phase: the controller vents the drive line; hydrostatic pressure pushes water into the bladder through a one-way intake valve.
- Discharge phase: the controller sends compressed gas down the drive line, squeezing the bladder from the outside and forcing water up the sample line.
- Cycling: the controller repeats fill/discharge cycles at a set rate, producing a steady low-flow stream — typically 100–500 mL/min for regulatory-compliant low-flow sampling.
How Does a Bladder Pump Compare to a Peristaltic or Submersible Pump?
ERE's peristaltic pump selection guide covers the suction-lift option for shallow, general-chemistry wells. A bladder pump is the next step up for depth and analyte sensitivity — and a submersible pump is the step up again for flow rate. Here's how the three compare on the factors that actually decide which one you need:
| Pump type | Mechanism | Typical depth limit | VOC/PFAS-safe? | Best for |
|---|---|---|---|---|
| Peristaltic | Suction (vacuum) lift through tubing | ~26–33 ft (8–10 m) | No — vacuum can strip volatiles | Shallow wells, general chemistry, metals, nutrients |
| Bladder | Pneumatic — gas squeezes an internal bladder, no gas/water contact | 500 ft (407) to 1,000 ft (Dedicated) | Yes — EPA/ASTM-recognized for low-flow VOC and PFAS sampling | Deep wells, VOC lists, PFAS programs, regulatory low-flow compliance |
| Submersible (electric) | Electric impeller/centrifugal, higher flow | ~120 ft (Solinst 415) | Not typically used for VOC-sensitive final sampling | Well development, high-volume purging, non-VOC parameters |
A 12V submersible pump moves far more water per minute than a bladder pump, which is why it's the right tool for developing a new well or purging large casing volumes — but for the actual low-flow sample once the well is stabilized, the bladder pump's positive-displacement design keeps the sample representative.
Which Solinst Bladder Pump Model Fits Your Well?
ERE stocks four bladder pump configurations, all sold through the water sampling pumps collection, each suited to a different depth, program size, or dedication strategy.
| Model | Max depth | Body | Best for |
|---|---|---|---|
| Solinst 407 SS Bladder Pump | 500 ft (150 m) | 316 stainless steel, PTFE or LDPE bladder | Standard low-flow or regular-flow sampling; meets US EPA VOC groundwater standards |
| Dedicated Bladder Pump | 1,000 ft (305 m) | Left in the well permanently | Deep wells and recurring monitoring rounds where redeploying a pump each visit isn't practical |
| Portable Bladder Pump | Well-dependent | Single-turn release head, quick-change bladder | Multi-well sampling rounds — field-swappable bladders and no-tool decontamination between wells |
| Solinst 408M Micro Double Valve Pump | Fits 1/2" (13 mm) tubing | Coaxial PTFE tubing, 3/8" (10 mm) diameter | Narrow-diameter wells and Solinst 403 CMT multi-level monitoring systems |
For PFAS-specific programs, specify the 407's compression-fitting variant (no Teflon in the wetted path) rather than the standard barb-fitting version — Teflon components are a documented PFAS cross-contamination risk in low-detection-limit sampling.
What Controller Do You Need to Run a Bladder Pump?
A bladder pump is only half the system — it needs a surface controller to cycle the compressed gas. ERE stocks three controller classes:
- Solinst 464 Electronic Pump Controller — microprocessor-timed fill/discharge cycles for precise low-flow rates down to 100 mL/min or less, with quick-connect fittings for dedicated well caps and portable reel units.
- 300/500 psi BP Controllers — higher-pressure regulators built for deep-well applications where standard controllers can't maintain flow against the head pressure.
- geocontrol PRO™ — a self-contained portable controller that replaces a compressor or nitrogen cylinder, useful for field crews sampling multiple wells across a site in one day.
How Do You Set Up a Bladder Pump for Low-Flow Sampling?
- Match the pump and bladder material to the analyte list. PTFE bladders for dedicated, high-integrity sampling; LDPE for lower-cost per-event bladder changes. PFAS programs use the no-Teflon compression-fitting variant.
- Lower the pump to mid-screen depth in the well, keeping the intake below the water table but above accumulated sediment.
- Connect the controller to the drive line and to a compressed air, nitrogen, or portable controller gas source.
- Set the fill/discharge cycle on the controller for a target flow rate of roughly 100–500 mL/min — the range EPA and ASTM D6771 specify for minimal-drawdown low-flow sampling.
- Purge and monitor water-quality parameters (pH, conductivity, turbidity, dissolved oxygen, ORP) until they stabilize per your program's low-flow protocol.
- Collect the sample directly from the discharge line once parameters have stabilized, minimizing sample handling and aeration.
For the broader equipment picture — water-level monitoring alongside your sampling program — see ERE's Solinst Levelogger guide and water level meters buyer's guide.
Need help specifying a bladder pump and controller?
ERE Inc. has supplied environmental and groundwater monitoring equipment to Canadian consultants for 30+ years — tell us your well depth, analyte list, and program size and we'll recommend the right pump and controller.
→ Request a Quote | 1-888-287-EREC | Browse Water Sampling Pumps | sales@ereinc.com
Frequently Asked Questions
What's the difference in depth rating between the 407 and the Dedicated Bladder Pump?
The Solinst 407 Stainless Steel Bladder Pump is rated to 500 ft (150 m). The Dedicated Bladder Pump is rated to 1,000 ft (305 m) and is designed to stay in the well permanently between monitoring rounds, rather than being redeployed each visit.
Can a bladder pump be used for PFAS sampling?
Yes, with the right configuration. Specify the compression-fitting, no-Teflon variant of the 407 rather than the standard barb-fitting model — PTFE (Teflon) components in the wetted path are a documented cross-contamination risk for low-detection-limit PFAS analysis.
What gas source does a bladder pump controller need?
Compressed air or nitrogen from a cylinder or field compressor, or a self-contained unit like the geocontrol PRO™ that eliminates the need to carry a compressor or gas cylinder between wells.
Will a bladder pump work in a low-yield well?
Yes — the fill/discharge cycle rate on the controller can be slowed to match a low-recharge well's yield, which is part of why bladder pumps are standard for minimal-drawdown low-flow sampling in tight-formation monitoring wells.
Related articles
- Low-Flow Groundwater Sampling: Peristaltic Pump Selection Guide for Canada
- Environmental Sampling Equipment Guide for Canada
- Solinst Levelogger 5 Groundwater Monitoring Guide
- Water Level Meters: A Buyer's Guide for Canadian Groundwater Monitoring
Lire en français : Pompes à vessie pour l'échantillonnage des eaux souterraines : guide de sélection