Mains Water and Well Water: Two Models of Management

On one side there is a user who pays no water bill because they have a well, but has never had what is in that water measured. On the other, someone connected to the mains who has never opened the subject at all, saying “it must be treated anyway”. The two situations are nothing alike; but what is missing is the same: data. Mains water and well water — that is exactly where understanding the difference between them begins.

This article compares the two sources impartially. It presents neither as superior to nor more objectionable than the other; it sets out that the two behave differently and so call for different approaches to treatment. And the conclusion reached is the same for both sources: the right answer starts with an analysis.

What Is the Basic Difference Between Mains Water and Well Water?

Mains water is treated centrally and monitored regularly by the competent authorities. With well water, monitoring the quality and treating it where necessary is entirely the responsibility of the user. The two sources have different profiles of content and variability, and so their approaches to treatment differ too.

The key idea in that definition is “responsibility”. The difference has less to do with the water itself than with who monitors it. On the mains a body takes regular measurements and works within a defined framework; on a well that job belongs to the user.

The second decisive difference is variability. Because mains water goes through a central process, it offers a relatively steady profile. Well water, drawn directly from underground, can differ with the geology and with the conditions of the season.

When those two differences are weighed together the picture becomes clear. A Mains water and well water comparison is not a ranking of “good and bad” but a comparison of two different models of management.

The Difference in Responsibility: The Most Critical Distinction

On the mains, water goes through a defined process before it is put into distribution and is monitored regularly. On a well there is no such mechanism; knowing what is in the water and treating it where necessary is left to the user’s own initiative. That is the most decisive structural difference between the two sources.

Let us make it concrete. In a household connected to the mains, the user is inside a defined framework even without knowing directly about the work done on the source side. In a household using a well, no such framework comes into play automatically.

That distinction does not run well water down. It says only this: in a household using a well, an analysis is not a choice but a necessity. On private wells, the US Environmental Protection Agency private wells resource offers a similar framework and stresses that well owners should keep up regular monitoring.

On the legal side care is needed. Drilling a well, permission to use it and the obligations that go with them vary by area and by regulation; the local authority and the relevant regulations should be consulted on that.

The Difference in Source: Surface and Underground

Mains water is generally taken from a central source, treated and delivered through a distribution line. Well water is drawn directly from underground; its content is settled by the rock and soil layers it passes through. So two wells can show different profiles even in the same area.

What is in groundwater is the result of a journey. Rainwater seeps into the soil, moves between the layers and dissolves part of the minerals it touches along the way. In an area rich in limestone the hardness can be high, while in a different geology the picture changes entirely.

So no “general” profile can be defined for well water. In the same village, the water of two neighbouring wells can show different content when they are fed from different depths.

On the mains the position is different. The source is processed centrally and put into distribution, and that means a more predictable profile. Variability on the user’s side generally arises not from the source but from the conditions of the plumbing and the tank.

That difference in source is also the basic explanation of why mains water and well water call for different treatment builds.

Figure 1: The different journeys of mains and well sources

The Parameters Seen Most Often in Well Water

The parameters most often assessed in well water are hardness, iron, manganese, turbidity, nitrate and microbiological load. Which of them come to the fore varies widely with the geology of the area and with the activities around it; so every well is assessed separately.

The headings below are the ones met with most often in well analyses:

The numerical values of those parameters vary over a very wide range from area to area, so it would not be right to give threshold values here. Suitability as drinking water is established by the relevant regulations and an accredited laboratory report.

Iron comes up particularly often in well water and divides into different forms of its own. We took up that distinction and the approaches to solving it in detail in our article on iron in water .

Which problem in well water is dealt with by which stage we examined in a separate article; for the build of the stages you can look at our treatment stages for well water . We do not repeat the stages in this article.

The Subjects Seen Most Often in Mains Water

The most common subjects in mains water are taste and odour from residual chlorine, hardness varying by area, and changes caused by the plumbing and the tank. Most of those arise not at the source but along the way the water travels before it reaches the user.

Residual chlorine is there to protect the water along the distribution line. That is not a fault but a deliberate practice; it is, however, the main source of complaints about taste and odour. We took up how it is removed at the point of use in our chlorine taste and odour article .

Hardness is a regional matter. In the same country, hardness can differ markedly between cities and even between districts. That explains why limescale is a problem in some households and never comes up in others. We took up the criteria for choosing on the softening side in our softening selection guide .

The third heading is change on the user’s side. The age of the building’s plumbing, the condition of the tank if there is one and how long the water stands can all affect the profile at the source. That effect is more marked in buildings with a tank; we examined the subject in our tank water quality article.

So being connected to the mains does not remove the need for an analysis entirely either. A sample taken at the point of use shows the real position at your own tap.

Why Is Seasonal Variability More Marked in a Well?

Because well water is fed directly from underground, it can be affected by rainfall, drought and activities in the surrounding area. Turbidity can rise after heavy rain, while the concentration of dissolved solids can change in dry periods. So a one-off analysis is not an adequate way of monitoring a well.

On the mains the central process largely balances out that fluctuation. On a well there is no such buffer; the conditions at the source show up directly for the user.

The main factors leading to variability in well water are these:

• Heavy rainfall: As surface water seeps into the layers, cloudiness and particle load can rise.
• Drought: When the water level falls, the concentration of dissolved solids can change.
• Activities in the surrounding area: Agricultural and industrial activity nearby can affect the content.
• Well maintenance: Protecting and maintaining the mouth of the well determines how far outside factors get in.
• The running of the pump: The pattern of draw and the depth can affect the amount of particles carried up.

That variability does not make well water problematic; it only shows that it calls for monitoring. For a well, a regular analysis is the only way to confirm that the system is working correctly.

The Two Sources Side by Side: A Comparison

The two sources differ in the monitoring mechanism, the responsibility, the level of variability, the typical problems and the treatment approach needed. The comparison is not a ranking of superiority; it shows the management requirement of each source.

The table below sums up the differences between mains water and well water heading by heading:

What the table shows is not that one source is superior to the other but that the two are managed differently. On the mains the work on the user’s side is limited to the point of use, while on a well the process is in the user’s hands from end to end.

So applying the same solution to the two sources would not be right. The next section takes up how the approaches differ.

Figure 2: Treatment approaches that differ by type of source

How Do the Treatment Needs Differ?

On the mains the solutions are generally focused on taste, odour and hardness; a carbon stage and, where needed, softening come to the front at the point of use. On a well the approach is broader: sediment filtration, iron removal where needed and an extra stage for microbiological risks are all assessed together.

The scheme that sums up the difference runs like this:

It is worth stressing why pre-filtration is essential on the well side: the particle load affects every stage behind it. On sources with a high particle load, sand units with automatic backwashing take on that job.

If a microbiological risk is identified, an extra stage comes onto the agenda. We took up how UV (ultraviolet) treatment works and what it does and does not do in our ultraviolet treatment article ; that stage is always positioned after the filtration.

For comprehensive well installations the system is sized for the project. In high-flow buildings, industrial well water systems .

Buildings Using Both Together

In villas, farms and some plants the two sources are used together: well water for the garden and as utility water, mains water on the drinking and kitchen line. The most critical technical point in that build is separating the two lines and preventing backflow.

Using both is a practical answer and a common one. Well water is preferred for garden watering, cleaning and technical use, while the drinking and kitchen line is left on the mains. In that way each source is used where it is strong.

But that build has one aspect calling for care on the plumbing side: the two lines must not mix. The lines joining, or backflow occurring, upsets the expected behaviour of both sources.

When the build is planned, these headings should be made clear: which points will be fed from which source, where the lines will separate, how backflow will be prevented, and which treatment stages will sit on each line.

In buildings of that kind, separate treatment builds are planned for mains water and well water . The well line works mainly on pre-filtration, while point-of-use solutions come into play on the mains line.

The Starting Point in Both Cases: An Analysis

Whatever the source, the right answer starts with an analysis. On the mains the sample is taken at the point of use so that the effect of the plumbing and the tank is assessed; on a well a full analysis and regular monitoring are needed. A choice made without an analysis rests on guesswork.

The right order is the same for both sources:

1. Take a Sample

   On the mains the sample should be taken at the point of use, and on a well directly from the source line. The sample should represent the real position.

2. Ask for the Right Parameters

   In well water, headings such as iron, manganese, nitrate and microbiological load should be requested separately; standard packages may not include them.

3. Assess the Report

   Which parameters stand out is established. Suitability as drinking water is assessed by the relevant regulations and an accredited laboratory report.

4. Match the Stages

   Stages to suit the problems identified are chosen. Adding an unnecessary stage creates cost, and a missing stage affects the result.

5. Keep Up the Monitoring

   In well use in particular the analysis should be repeated regularly and the system confirmed to be working correctly.

We took up step by step how to take a sample and how to read the report in our water analysis guide step by step; we do not repeat the process here.

Water Point Su Arıtma Teknolojileri operates from Esenyurt, İstanbul under its founder Ali Genç, with more than 20 years of experience in the sector.

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