A TDS meter cannot tell you whether tap water is suitable for your espresso machine. It gives a rough conductivity-based estimate, not a breakdown of hardness, alkalinity or chloride. Two waters with the same display reading can behave differently.
Get the machine's requirements first
Look for the water specification in the manual or ask the manufacturer. Keep the units and measurement basis attached to each number. Hardness and alkalinity are often expressed as mg/L as calcium carbonate; a reading in another unit needs conversion before comparison.
La Marzocco publishes its own water requirements, for example. Those limits belong to its machines; they are not permission to use the same recipe in every espresso boiler. Requirements may also change between products or manuals. Check the current document for your model.
Ask for the measurements that answer your question
For a practical starting record, obtain total hardness and alkalinity, then check what the manufacturer says about chloride, pH and other parameters. A municipal report is useful background, but it may describe a supply region rather than the water coming from your kitchen tap.
A drop-count test kit can help measure hardness or alkalinity at home if used as instructed. Check its expiry, sample volume and units. Broad colour strips are useful for screening, but an ambiguous colour should not become a precise claim such as "exactly 73 ppm." If a result is near a limit, use a more appropriate test or qualified water service.
Measure the water you will actually use
Test after any filter or treatment. Record the date, cartridge age and source. "Tap water" is not a stable recipe if a cartridge has just been replaced or the supply changes seasonally. Water from a domestic softener also deserves its own test rather than an assumption that it is automatically suitable.
Use a record such as: "Kitchen cold tap, new cartridge, total hardness 80 mg/L as CaCO3, alkalinity 65 mg/L as CaCO3, kit brand and date." Those numbers are an example of how to write a result, not a universal target. Compare your actual results with your manufacturer's limits.
Decide what to do with the result
If the measurements meet the machine's requirements, you may not need a complicated treatment system. If one parameter is outside them, choose treatment for that parameter. A carbon filter chosen for taste is not evidence that hardness is now acceptable.
If you do not know the required chloride limit or cannot measure it adequately, ask for advice before feeding a costly machine. The water-filtration guide explains the next decision. Do not add salts to an unknown starting water merely because an online calculator can produce a number.
