Testing Untreated Well Water: Frequency and Parameters

It is essential that the well water be tested before any significant quantity is consumed. Lead and arsenic seem to be the most reported "nasty" issues worldwide. Refer to the "red wells" in India that are the result of a well intentioned aid program.

Follow-up testing frequency would depend (for me) on the water source itself. If the well is supplied from surface water that has percolated to bedrock and is naturally making its way downhill, then it could have contaminants from surface activity incorporated into the stream and become contaminated in a relatively short time. Similarly a sand bed drawing water from a nearby river or watercourse.

Wells that penetrate impervious layers (Some might distinguish these as bores rather than wells) are probably drawing water from a relatively quarantined water source and are less likely to be contaminated by surface activities. These also would not have issues with biological components.

It really seems to me like a "risk assessment" should be done on each specific well rather than a general statement.

I have given you a GA for recognizing the variability of ground water. The biological components of deep wells are always misunderstood. A well should be viewed as an intrusion into a geological formation. There is much biological activity in the subsurface water. You would be correct if the only consideration were E.coli or total coliform. Ground water has a plethora of biological activity including iron and manganese bacteria, sulfate reducing bacteria (SRB), methane bacteria, Heterotrophic (HPC), etc. Normally these bacteria sit in a groundwater regime and are limited in growth due to space and nutrients. The well or intrusion provides a large surface area and the pumping creates a nutrient delivery system. Now the well is a bio amplifier of the insitu ground water microbiology.

I think what I am looking for is some general chemistry and microbiology that will characterize most ground water anywhere. I have always been surprised at the parameters that can show up unexpectedly. Think about the water supply as your own and what you would test for say once every 10 years. If these results indicate something, then more frequent testing may be warranted for certain parameters. Rural homeowners seem to think that you can get results cheap but reality can sink in quickly. If you are recommending parameters try to keep costs down; but, don't sacrifice the knowledge just to save a few bucks. What you don't know can hurt you. A single private well can be more complex than many municipal wells. And you are right each case has its own testing requirements.

I often have to help customers quantify their well water quality. In this part of the world, I would not be comfortable with anything less than testing twice a year (once towards the end of the dry season, once towards the end of the rainy season), and nothing less than a full laboratory test suite (biological as well as chemical). Two issues here- there are significant seasonal differences in shallow ground water quality due to significant differences in aquifer recharge rates, and, secondly, there is a lot of development going on in this country, and someone drilling a new well, say too close to a septic leach field, for instance, can contaminate an aquifer for all other users. There is inadequate control over who can drill wells where in this country. I have also seen negative effects on an aquifer resulting from the installation of a small hydro electric facility that significantly modified the drainage patterns in the area (wells were about 5 km from the hydro facility. Changes included decreased recharging rate, and higher mineral content, although in this case, there was no increase in the nasty stuff). Most of my experience has been with shallow wells, and tapping in to "fossil" water would probably involve different criteria. Unfortunately, most of those that rely on shallow wells do not have the $350 every six months for a complete laboratory analysis...

Trying to come up with "universal" rules is very difficult. How well does the local authority control well-drilling? Can anyone just punch a hole in the ground without a permit? What sort of development activity is going on in the area? What are the seasonal effects that one must deal with? How much health insurance can the well owner afford? Well water testing is, essentially, health insurance...

Well stated (pun intended). I do not have much of a handle on water in tropical areas. Once an original suite of parameters have been completed, detecting changes in seasonal water may be as simple as monitoring conductivity during rainy seasons. In an area with few rules and where we depend on common sense of the well driller, there may be lots of room for variability in quality. I live in an area with growing ever restrictive rules on well construction. However, I do remember a time when I considered the rules of well construction very poor and designed my own for many government projects I had worked. I like to think that it started a movement of knowledge among well drillers and rule makers.

Getting testing done on private wells remains woeful even when the department of health offers free bacteria testing. Having Chemistry testing at $500.00 is a difficult to almost impossible job to convince existing homeowners with wells. The regulations on testing should likely apply to new wells and at the time of property transfer (already in use in some locations). Smart lawyers should ask new buyers to consider water testing but don't push the idea in case of loss of their client. It seems to come down to dollars and "sense".

Just a small point for clarification. When I mentioned deep bores through impervious layers, I was thinking of Artesian bores and similar as seen in Australian outback. Typically these are drawing water from 1000m or deeper, have no inflow from the surface (not even air).

I have not heard of any "biological" action in those wells, but could stand corrected.

There are the occasional aquifers that are biologically "clean" but very rare. In the US southwest, it is reported that dissolved oxygen (DO) can still be measured in some very deep wells. The reason for still finding DO in these deep wells is that there is little or no organic carbon entering the aquifer during periods of recharge. Oxygen is a primary source of respiration for microbes. Once oxygen is depleted then the bacteria move on to other less efficient ways to respire with in order of availability nitrates, manganese, iron, sulphates, and Carbon dioxide. Carbon dioxide is a reduced byproduct of each cycle. Once oxygen is depleted, the water quickly turns into a reduced environment. This activity is driven by a food source and nutrients. Organic carbon (measured as TOC) is required and if absent as in the US southwest will mean little biological and lead to pristine aquifer conditions. Nutrients in the form of phosphorous (arguably in any form), nitrogen, and trace elements. Organic nitrogen can be measured by subtracting ammonia from total Kjeldahl nitrogen.

The deep aquifers in Australia do not seem similar as you indicate no DO present. That means there are reduced conditions leading to other cycles such as manganese, iron, and sulphide production. There may even be methane present in wells that are very reduced (likely a depleted supply of sulphate). All this is meant to suggest groundwater microbiology is invasive and present in almost all wells. The activity can be measured and observed in chemical and microbiological testing. Deep wells are very ancient water from connate conditions. As such often the water is saline and highly mineralized. The regional aquifer where I live is about 800 feet deep and has a conductivity of 12,000μS/cm (salty). If my recollection is correct similar conditions are found in Australia. Potable water must be a very valuable commodity in Australia. FYI

A thousand meter deep well!! That has got to be expensive for a domestic well...I guess testing should just be a drop in the bucket in the overall scheme of getting a potable supply of water.

At my in-laws home they have a private well I test annually for the following:

pH, TDS, Cl (NaCl contamination), Ca (Hardness), E. coli, Fe, and S

Initial testing and every ten years:

Above state compounds, plus

RCRA 8 (Heavy Metals), Pesticides (land was a old orchard), and Gasoline/Diesel Range Organics( this was because this was a gas station 1/4 mile up stream of our well).

The last round of testing was for everything cost about $320, annual testing was around $77 all from a third party accredited lab. I took my own samples and hand delivered them.

That is a good price for testing and very cheap insurance for peace of mind. Not sure if NO3 and Uranium ion are of issue but could easily be verified by the lab. I usually suggest pumping the well to remove at least 3 volumes of water from the well prior to sampling and the testing of untreated water directly from the well. I would also recommend the periodic (every few months or as required) disinfection of the well with a product like Wellrific. Wellrific is a hydrogen peroxide compound that is better to remove biofilms than chlorine compounds.

The well is ~400 feet deep the pump is about at 350 feet and the water level is around 15 feet from the surface. It has never run dry so I usually let it run about a hour then grab the sample.

Knock on wood it's been clean so far (15 plus years), a little high on the hardness is about it (most likely the local limestone). I did hook up an UV disinfection system to their plumbing just in case.

I've had the house tested several times for radon and it is well in the safety margins.

We have city water, I trust my in-laws well any day over the city. I have different filters at home to help with the taste.