Testing Your Water in Los Cabos: Use the Right Test for the Question

The short answer

There is no single home water test that answers every question.

If you want to know whether your water is hard, measure hardness directly. If you want to know whether a disinfectant residual is present, measure free chlorine. If you want to know whether water is microbiologically acceptable, use an appropriate microbiological laboratory test. If you want to know overall mineralization, a TDS/conductivity meter is useful.

The most common testing mistake in Cabo is treating a TDS reading as a hardness or safety result. It is neither.

MirAqua principle: test the problem you are trying to solve.

The five questions a Cabo property should separate

1. How mineralized is the water?

Use TDS or conductivity as a screening/comparison tool.

Useful for:

• comparing samples over time;
• noticing a large change after a different delivery or source;
• comparing RO feed and product water.

Not useful for proving:

• hardness concentration;
• microbiological safety;
• the identity of a specific contaminant;
• the exact water source.

2. How hard is the water?

Use a hardness titration/drop test or laboratory hardness method and report the result as mg/L as CaCO3 or grains per gallon (gpg).

Hardness is primarily calcium and magnesium. It is the measurement that matters when evaluating scale, water-heater fouling, detergent performance, or a water softener.

Conversion: 1 gpg ≈ 17.1 mg/L as CaCO3.

Read the Los Cabos hardness guide →

3. Is a disinfectant residual present?

Measure free chlorine with a suitable test kit or photometer.

A chlorine result is a measurement at a particular place and time. Residual declines during storage at a rate that depends on starting concentration, temperature, organic/chlorine demand, tank surfaces, sediment, biofilm and other chemistry.

For stored household water, the residual may fall below a useful level in hours to several days depending on conditions. Do not assume that every Cabo cistern follows the same 2-, 3-, or 5-day clock.

A better routine is to test:

• at or soon after delivery;
• again after roughly 24 hours;
• again after 48–72 hours when learning a property’s behavior;
• later if the tank has low turnover.

Why water age matters →

4. Is there a particulate/sediment problem?

Use visual inspection plus turbidity where a quantitative result is useful.

Visible sand, silt or debris tells you there is a particulate problem, but appearance alone cannot establish microbiological safety. A sediment filter can protect pumps, valves and downstream treatment, but it does not soften or disinfect water.

5. Is the water microbiologically or chemically acceptable for the intended use?

Use an appropriate laboratory analysis.

Depending on the question, this may include:

• E. coli / appropriate coliform indicators;
• nitrate;
• fluoride;
• arsenic, lead or other metals;
• chloride, sulfate, sodium and other dissolved ions;
• hardness and alkalinity;
• turbidity and other physical parameters.

The exact panel should match the use case and the applicable drinking-water requirements. A TDS meter cannot substitute for this.

A practical Cabo testing ladder

Level	Test	Best use	What it does not establish
Screening	TDS / conductivity	Mineralization and sample comparison	Hardness, safety, contaminant identity
Scale	Hardness titration	Ca/Mg hardness and softener sizing	Microbial safety
Storage	Free chlorine	Residual at a specific time/place	Absence of all pathogens
Physical	Turbidity / inspection	Suspended particles and clarity	Dissolved chemistry or safety by itself
Diagnostic	Certified/appropriate lab testing	Microbiology and specific chemistry	Future quality after storage or treatment changes

What to test before buying treatment

If the primary complaint is white scale, test hardness before buying a softener or conditioner.

If the complaint is taste or odor, identify whether the issue is chlorine, sulfur, organics, iron/manganese or something else before choosing media.

If the concern is drinking-water safety, use appropriate microbiological and chemical testing instead of relying on TDS.

If the concern is dirty water after pipa fills, inspect the storage system and particulate load, then size sediment filtration for the actual fill method and flow.

If the concern is stored-water hygiene, inspect the cistern/tinaco, review cleaning history and measure residual rather than assuming a calendar-based chlorine life.

Source water vs. water at your tap

A groundwater monitoring result, a pipa source test and a kitchen-tap test answer different questions.

A property can receive acceptable source water and still experience changes during transport, storage or building plumbing. Likewise, a raw groundwater monitoring result should not be described as the quality of every municipal or pipa-delivered sample.

When diagnosing a property, useful sampling points may include:

1. incoming/source water when practical;
2. cistern or tank outlet before treatment;
3. treated water after the relevant system;
4. drinking tap if that is the end-use question.

How MirAqua should use testing

Testing is not an add-on designed to justify a bigger system. It is how we avoid selling the wrong system.

A simple property assessment can route customers into different solutions:

• sediment only;
• cleaning/storage management;
• hardness control;
• taste/odor treatment;
• point-of-use drinking treatment;
• an engineered combination where the measurements justify it.

That means some customers should spend less, not more, after testing.

Frequently asked questions

Is 700 ppm TDS dangerous?

A TDS number alone cannot answer that. It indicates overall dissolved mineral/ionic content, not microbiological safety or the concentration of a specific regulated contaminant.

Does a TDS meter measure hardness?

No. TDS and hardness can move together in some waters, but they are different measurements. Use a hardness test for calcium/magnesium hardness.

Can I identify my pipa source from TDS?

Not reliably. TDS can show that two samples are materially different, but multiple sources can overlap and a source can change over time.

How long does chlorine last in my cistern?

There is no universal Cabo number. In stored household water it can fall below a useful residual in hours to several days depending on the starting residual and chlorine demand. Measure your property rather than assuming a fixed timeline.

Does zero free chlorine mean the water is contaminated?

No. It means there is no measurable free-chlorine residual at that sampling point/time. Microbiological testing is required to determine microbial quality.

Should I test before installing RO or a softener?

Yes. A softener should be sized from actual hardness and usage. RO design depends on feed-water chemistry, pressure, pretreatment and the actual drinking-water objective.

Start with the question

Tell MirAqua what you are trying to fix — scale, sediment, storage, taste/odor or drinking water — and the testing plan should follow from that question.