Water Level Data Loggers – Why Standards are Required

If you thought that you could rely on the manufacturer’s specification to compare the accuracy of water level data loggers, think again. A comprehensive research paper testing the performance of 14 leading brands has highlighted a large range of inconsistencies. Peter Dumble, Technical Director at Waterra In-Situ, reflects on the report.

Peter Dumble, Technical
Director, Waterra In-Situ

The 2011 paper by Sorenson and Butcher of the British Geological Survey “Water Level Monitoring Pressure Transducers – A Need for Industry-Wide Standards” (Posted from Ground Water Monitoring & Remediation with permission of the National Ground Water Association. Copyright 2011) has highlighted some key issues for everybody involved in ground water and surface water level monitoring.

The paper looks at the results of comprehensive laboratory and field tests on 14 leading brands of pressure-transducer based water level logging devices, and the results are troubling.

• In laboratory tests poor temperature compensation was a particularly significant issue, with 5 sensors showing substandard performance.



• In field tests variations in pressure recording during extreme temperatures or rapid temperature changes were also outside of the stated ranges for several sensors. The authors highlighted two factors as causes of inaccuracy:
  - Sensor design and the efficacy of correction algorithms
  - Lack of thoroughness by manufacturers in instrument calibration



• Field testing also exposed the problem of drift, with sensor accuracy deteriorating over time. One high pressure sensor drifted by up to 181mm. The paper comments that drift “may be the key accuracy determinant during long term water level monitoring”.

We fully support the paper’s call for industry wide standards for both calibration and specification. Hydrogeologists, geotechnical consultants and environmental consultants need to be able to make their choice of equipment based on actual performance and the real capability, not on untested supplier aspirations. Monitoring organisations and field engineers should be able to trust the measurements they are receiving, especially as the trend for reductions in the number of site visits accelerates.

At Waterra In-Situ we are proud to be judged on performance. All of our water level and water quality monitoring equipment is precision engineered and features solid titanium housings and a choice of both ceramic and titanium sensors for sustainable long term deployment. Level sensors are calibrated across their full operating temperature and pressure range to ensure that they conform fully to their stated accuracy. Factory calibration is conducted to fully traceable external national standards (NIST - National Institute of Standards and Technology).

As a result we are confident that we state the accuracy specifications of our loggers, that's what you will get in the real world.

To find out more about the testing and calibration of the Waterra In-Situ range contact our support team on +44 (0) 121 733 7743 or email sales@waterra-in-situ.com.


There is more information on the accuracy and calibration of our loggers on the website and we have a one day data loggers training course on March 28th 2012 that focuses on improving the accuracy of water level measurement. 

Exceptional Demand for Belfast Groundwater Sampling Training

We were delighted at the level of interest shown when running the groundwater sampling training course in Belfast on 13th & 14th December 2011.

This course attracted more delegates than to any of our previous courses leading us to run the course on two separate days in order to meet demand! We were fortunate in attracting deegates from a wide range of sectors including environmental consultants, regulators, universities, local authorities and water companies.

Delegates gained the latest insights into groundwater sampling methods and a better understanding of regulatory guidance. The content must have been good because we received an aggregate score of 1.2 on the Geological Society CPD assessment scale where 1 is excellent and 5 is very poor. Thank you to those who were there!

The session was lead by Hydrogeologist, Peter Dumble, Waterra In-Situ’s Technical Director, who is the principal author of the current Environment Agency and SEPA guidance for monitoring leachate, groundwater and surface water at landfill sites. Peter was full of praise for the course audience:

“Groundwater quality monitoring is a vital safeguard to ensure water supply for public consumption, agricultural, industrial and and ecological use, whilst quality status is an important part of the monitoring and reporting requirements of the EU Water Framework Directive. These interests were reflected in the backgrounds of all those present. 

The high attendance, attentiveness of delegates to our presentations and demonstrations, and the quality of the questions I received were outstanding. There was particular interest in low flow and passive sampling methods with many concerns expressed at the practicality of using low flow and the requirements of regulators when switching between methodologies".

Delegates provided some good testimonials for the course:

‘Good to mix up some practical knowledge with the theory. Knowledgeable team presenting’

‘The course presenter was very knowledgeable which helped when I had queries and questions’

‘Very good and interesting – provides a lot for thought!’

Our next half day Groundwater Sampling course will be in Warrington on 8th February 2012 followed by our annual 1 day course in Birmingham on 23 May 2012. We have already almost filled the course in Warrington, so book now for this event!

For more information and to download a booking form for Warrington or Birmingham visit the training pages on our website.


Waterra In-Situ - Check out our range of active and passive skimmers for the removal of LNAPL layers

Pneumatic Slug Testing: An New Approach for Hydraulic Conductivity Monitoring?

Conventional slug testing offers some major advantages over pump tests in site investigations but there are some issues associated with projecting slug test permability values to larger aquifer volumes. Could pneumatic slug testing provide an alternative?

Slug testing using a known volume of water or an item that displaces a measured volume has become a standard tool in the hydrogeologist's or engineer's kit bag in recent years. The approach offers a number of advantages over standard pump-based tests because it is easy to implement in the field, offers large cost savings, and it will work in low flow environments.

Conventional slug testing has improved our ability to determine hydraulic conductivity, and consequently made a major positive difference to site characterisation across a range of applications. However there are some drawbacks, particularly related to the need for the insertion of a water sample or a solid slug. For instance;

• The pressure wave caused by insertion may impact data accuracy.


• Slugs may not manoeuvre around well or borehole casings


• It may be difficult to deploy a slug large enough to create sufficient displacement for measurement.

Pneumatic slug testing offers an interesting new option to overcome these issues because, as the name suggests, no physical slug is used. Instead the well or borehole is sealed and air is used to pressurise the water column. When equilibrium is reached between the pressure in the water head and the well then de-pressurisation takes place and a data logger can measure the resulting changes in water level.

Apart from removing or reducing the problems associated with physical slug insertion, pneumatic slug testing also provides near instantaneous slugging events, which is very important in achieving the best possible accuracy.

Waterra In-Situ Technical Director, Peter Dumble, believes that pneumatic slug testing will in time become a preferred mechanism for monitoring hydraulic conductivity in monitoring wells and boreholes.

"This method of hydraulic conductivity testing has some clear advantages over both pump testing and conventional physical testing. In the short term I can see some important niche applications for the approach and over time we are likely to see it become the method of choice in the industry"

To find out more about pneumatic slug testing download our datasheet (PDF opens in new window) or call the Waterra-In-Situ's technical support team today on +44 (0)121 733 7743.



Waterra In-Situ - For a full range of oil water interface level meters

Monitoring water and DNAPL levels in real-time

Monitoring DNAPL levels in real-time has always been a challenge. Now with the help of the In-Situ Level TROLL® 500 instrument there is an effective way of keeping track.

DNAPL (dense non-aqueous phase liquid) contaminants have the unpleasant property of sinking below the water table and creating the potential for long term environmental problems.The difficulty for organisations who are engaged in the monitoring or remediation of brown field sites is that DNAPL materials such as chlorinated solvents, creosote or oils are simultaneously very common but have a slow migration profile. As such the impact on aquifers may take some time to show through.

The Level TROLL® 500 instrument provides an accurate method of providing data on the thickness of DNAPL levels in real-time and, if required, over the long term. The installation requires two devices; one for the DNAPL layer and the second in the water column. This allows the thickness of the DNAPL layer to be calculated by comparing the difference in density between the two liquids.

The Level TROLL® 500 has some very important features that allows it to cope with hostile conditions and remain operational for an extended period ;

• Titanium casing


• TROLL® Shield antifouling system


• A battery pack with typical life expectancy of up to 10 years

Waterra In-Situ Technical Director, Peter Dumble, believes that this use of the Level TROLL® 500 could have some important benefits in the remediation sector:

"Without a clear understanding of a site's DNAPL profile it is very difficult to choose the most appropriate remediation technique. What we have here is a mechanism that maximises the chance of getting it right first time."

To find out more about the DNAPL measurement procedure and the layer calculation equation download our datasheet (PDF opens in new window), take a look at the Level TROLL® 500 page on our website or call the Waterra-In-Situ's technical support team today on +44 (0)121 733 7743.


Waterra In-Situ - Experts in passive groundwater sampling techniques.

Low Flow Sampling with Advanced Data Outputs

Waterra In-Situ's new Low Flow System combines advanced low flow groundwater sampling capability with accurate and timely reporting functionality.

Low Flow System in Action

The system comprises a TROLL® 9500 Water Quality Instrument, RuggedReader® Handheld PC, a flow-through vessel with baseplate, Flow-Sense Software, and other accessories.

The core benefits of low flow groundwater sampling are supplemented by sophisticated data collection, monitoring and reporting features. The ability to automatically collate well and pumping information, set stability limits on key water quality parameters, and automatiacally record calibration and sampling data simplifies quality control AND improves conformance to regulatory standards.

Peter Dumble, Waterra In-Situ's Technical Director and Hydrogeoloist, sees the system as a major step forward:

"The technical case for low flow purging prior to groundwater sampling is well established for use in short-screened monitoring wells and boreholes and has been given increased prominence in the recent update of BS10175:2011 for use in contaminated land investigations. 

This system provides an elegant operational tool for adopting and recording the whole low flow sampling process. Engineers, consultants and hydrogeologists will welcome both the reducuction in the time it takes to create base reports and the improvement in quality control and accuracy of the process."

The system is easy to set-up and operate and is available to purchase or for rent. You can see just how easy it is to use by looking at the video below.





For more information on Waterra-In-Situ's Low Flow System call our technical support team today on +44 (0)121 733 7743.



Waterra-In-Situ - Rugged dip meters for well and borehole level measurement

Belfast Groundwater Sampling Training - Last Call

Half Day Groundwater Sampling Methods workshop in Belfast.

Waterra groundwater workshops are
CPD accredited.

Waterra's Groundwater Sampling Methods course is your opportunity to see a variety of low flow and passive (no purge) sampling methodologies and equipment in action.

We are delighted to be holding a half day workshop in Belfast, Northern Ireland on 14th December 2011 at the Jury's Inn, Great Victoria Street.

There has been a lot of interest in the course and only a couple of places are available so call us today on +44 (0)121 733 7743 to book your spot or visit the Waterra training page on our website for more details .

The courses are accredited by the Geological Society for CPD with discounts available for Geological Society Members and for multiple bookings.

Waterra In-Situ - Leading supplier of low flow groundwater sampling and purging equipment

Improved Rental Fleet - Groundwater Equipment

Waterra are delighted to announce the expansion of our range of rental equipment for groundwater and surface water sampling and monitoring.

Groundwater equipment rental range

Weekly hire of this equipment represents a convenient, cost effective alternative to purchasing, while for many of our customers rental has been a great chance to try before they buy.

All of our rental equipment is thoroughly cleaned, calibrated and tested before it leaves our warehouse in Birmingham and it can be delivered direct for immediate use.

Waterra MD Jonathan Trelfa suggests that rental is a sensible financial option:

"Our clients like this approach because it reduces their capital overhead and generates savings in storage, service and repair costs. It makes a great deal of sense in situations where accurate sampling and monitoring activity is important but on a medium to long term cycle such as environmental assessment and construction projects. "

We offer an 8 day rental package (inc. one weekend) to ensure that you get the most from your equipment hire. If you need assistance then our technical staff are available to take you call during office hours.

Our ALL NEW Rental Equipment range includes:

• The advanced TROLL® 9500 multiparameter water quality instrument
  Including our highly acclaimed Low "Flow Sense" package to help you manage and control low flow groundwater sampling professionally and reliably.



• Level TROLL® level and temperature data loggers
  Including both non-vented and vented systems using our top of the range Titanium Level TROLL 500 and 700 sensors for highly stable and accurate data every time, regardless of temperature variations.



• Aqua TROLL® conductivity, level and temperature logger
  Including dynamic density compensation. A best in class non-vented or vented logging system - ideal for salinity monitoring in coastal waters, seawater and groundwater.



• Easy Load II peristaltic groundwater sampling pumps
  Easy-change tubing system make this pump quite simply the best low flow sampling pump on the market! For use in any depth of borehole where water levels are less than 8 metres below ground level.



• WaSP F1 Low Flow pump controller
  For perfect low flow control of any 12V submersible pump. Use with any 12V sampling pump including Waterra's own WaSP 12V pumps.



• Powerpack PP1 inertial pump actuator
  For use with Waterra Inertial Pumps - the most efficient and economic pumping mechanism for traditional purging and sampling of groundwater boreholes.

Check out the groundwater equipment rentals page on our website for more information or call our technical support team today on +44 (0)121 733 7743.

Waterra In-Situ - For the full range of MiniRAE PID detectors