Many water treatment companies offer a free test at your kitchen sink. A technician pulls out a few vials, strips or a handheld meter, and a few minutes later you are looking at a set of numbers and a recommended system. The test itself is not the problem. The problem is that the numbers often become the whole case for a purchase, and most homeowners never ask what those numbers can actually support.
This guide is for the moment between the demonstration and the signature. It tells you what to ask, what to write down, and which questions the test cannot answer no matter how well it is done.
Know what a sink-side test usually covers
On-site kits and meters typically look at a short list of things that are easy to read quickly: hardness, chlorine, iron, pH, and a general reading of dissolved material. Some providers add a few others. These can be genuinely useful. Hardness, for example, is one of the main inputs to sizing a softener, and an iron reading helps decide whether a well needs extra treatment stages.
Ask for the list before the test starts, not after. If the technician cannot tell you exactly which substances will be measured, you will not be able to tell which ones were skipped.
Be careful with the dissolved-solids reading
A common demonstration uses a handheld meter that shows a single number for total dissolved solids. The meter generally estimates this from how well the water conducts electricity. It does not identify what is dissolved. Harmless minerals and unwanted contaminants can both raise the number, and some things you might worry about barely move it at all.
So a high reading does not prove your water is unsafe, and a low reading does not prove it is safe. Ask the technician directly: what does this number tell me to do, and what does it not tell me? If the answer jumps straight to a product, push back and ask what specific problem the product is meant to solve.
Ask where the sample came from
The same house can give different readings from different taps. Before you accept any result, find out:
- Which tap was used, and whether it was cold water.
- Whether the water ran for a while first or was drawn right away.
- Whether the tap sits before or after any treatment you already own, such as a softener or a filter.
- Whether the tap has a screen or aerator that could trap sediment or change the result.
A sample taken after an existing softener tells you how that softener is performing, not what your incoming water looks like. A sample taken from a hot tap tells you about your water heater as much as your supply. Neither is wrong, but each answers a different question, and you should know which one you got.
Get the readings in writing, with units
Ask for every result written down with its unit and the method used. Hardness is reported in more than one unit, and a number without its unit is easy to misread when you later compare it to a lab report or a second quote. Also ask what level the provider considers a problem, and why. A recommendation should connect a specific reading to a specific piece of equipment. If it does not, the test was a demonstration, not an assessment.
Ask what the test did not check
Some concerns generally need a laboratory rather than a sink-side kit. These include bacteria, nitrate, lead, arsenic and many other contaminants. If any of these worry you, say so and ask how the provider would handle them. A fair answer is that they need a separate lab test, and that equipment should not be chosen until you have the results.
The right path depends on your source:
- City water: your utility publishes water quality information for its system. Compare the provider's readings against it, and ask the provider to explain any gap. Remember that the water can change between the utility's system and your tap, so your own plumbing still matters.
- Private well: nobody is testing your water for you. A laboratory test with a clear list of what was analyzed is a much firmer basis for a purchase than a quick kit.
Ask who benefits from each result
You do not need to assume bad faith. But a person paid when you buy a system has a natural reason to read ambiguous results toward a purchase. Ask these questions plainly:
- If my results had been normal, what would you have told me?
- Is there any result here that does not need equipment?
- What would you recommend if I only treat the one problem I actually noticed?
- Will you put the recommendation, the readings behind it, and what the system is expected to change in the written quote?
The last question matters most. If the quote states only the equipment and the price, the connection between your water and the purchase lives only in a conversation.
Take the numbers home and check them
You are allowed to leave without signing. Use the time to do three things:
- Have a certified laboratory run any test that matters for health, and compare its report to the sink-side numbers.
- Get a second provider to test the same water, and compare readings, units, tap location, and method before you compare recommendations.
- Write down the specific problem you want solved, such as scale, staining, taste, or odor, and check that each proposed piece of equipment addresses one of them.
If you want to see how we think about judging providers beyond their sales process, read How We Rate Water Treatment Providers. If you are in the St. Louis area, the St. Louis Water Treatment Ratings page lets you compare the providers you may be considering.
A short checklist for the visit
- Which substances will you measure, and which will you not?
- Which tap, and was it before or after existing treatment?
- What are the results, in writing, with units and method?
- What does each result mean for my decision, and what does it not mean?
- Which concerns need a lab, and will you wait for that result before recommending equipment?
- Will the written quote name the problem each component is meant to solve?
A good test gives you facts you can carry to another provider and still get the same answer. If the information only works inside one sales conversation, treat that as a reason to slow down.