Confused by water? Our experts select the best water flow meter for each type.

Water is a broad term in the flow meter industry. We define each type of water technology and give you a few tips to help you understand water and water flow meters better.

Tap water

Tap water, potable water, tapolene = drinkable water.

This will  contain a selection of minerals and should have harmful viruses and contaminants removed. By far the most metered fluid on the planet by dint of the millions of domestic meters installed in most western countries. Meter selection is equally wide. Almost all  metals and plastics can be used in contact with water except for the relatively few that corrode – like iron or steel – which can be protected by a painting or coating process. Positive displacement meters and multijet pelton wheel meters are used in domestic settings depending on the required turndown.  Electromagnetic meters used for higher flows – but not applicable for many of the applications below where conductivity dwindles.

Distilled Water

This is a form of purification and refers to water that has been processed by heating to over the boiling point. The steam is then captured and cooled to produce liquid distilled water. This is the most popular form of purification process, and the end result is a very pure product. This method eliminates bacteria, organic and inorganic particles, viruses, minerals, and other contaminants from water, and the water must be preserved in a sterilised jar after it has been through this process to preserve its purity. Salts, metals, and minerals are removed during the process. As this form of water is very pure it will seek to leach out stray ions from the vessels or pipes that is within. It should be kept in glass. Plastic Turbine or Pelton Wheel, Transit time Ultrasonic clamp on flow meter.

Demineralised or Deionised Water

Demineralized water is a less expensive method of water purification that actually refers to any water that has had minerals and salts removed from it. This form of water is used in applications that need low conductivity or low salt content. Water is demineralized by moving it through specially formulated resins. The resin is engineered to exchange ions in water, resulting in a chemical composition that is identical to pure water. Though demineralized water is almost devoid of minerals and related substances, very small quantities of dissolved minerals will still be present. However, advances in demineralization technology ensure that the end product is very high quality water. Perhaps less sensitive than distilled water, we would still recommend: Plastic Turbine or Pelton Wheel, Transit time Ultrasonic clamp on.

Sea WaterBrackish water, sea water, salt water and brine

All considered to be salty water, the amount of salt does vary considerably; this is known as the amount of Totally Dissolved Solids (TDS) and is measured in milligrams per litre. Brackish water varies from 1,000 to 10,000, salt water from 10,000 to 35,000 and brine (or sea water) is greater than 35,000 mg/l.

Sea water is very aggressive to stainless steel particularly 303 and 304. 316 is better and needs to be electropolished, as a minimum. Sea water velocity affects corrosion rates.

Titanium is normally the answer if the meter is permanently immersed and/or the velocities are low. This leads to plastic meters being selected more often and as low as pressures are low. Plastic Turbine or Pelton Wheel, Transit time Ultrasonic clamp on. Electromagnetic meter with titanium or similar electrodes.

>>read more on our electromagnetic flow meters

Ultra Pure Water (UPW)

measured in ppb or ppt. Some processes require ultrapure water where the water is treated to the highest levels of purity. The impurities are measured in parts per billion (ppb) or parts per trillion (ppt) and are typically used in the manufacture of semiconductor wafers and pharmaceuticals. The main guides to quality are ASTM D5127 “Standard Guide for Ultra-Pure Water Used in the Electronics and Semiconductor Industries” and SEMI F63 “Guide for ultrapure water used in semiconductor processing” but UPW in pharma will be to a different specification. As with distilled water selection of the flowmeter is critical. Plastic bodied meters with ultrapure materials are just behind clamp-on ultrasonics as favourites.

Bottled WaterBottled water and mineral water

These are much like tap water except either drawn from a particular spring or built from pure water by the addition of minerals to achieve a specific taste. Gas in the form of CO2 may be added to preserve the minerals or, in higher quantities, just to add some fizz. For metering, see tap water recommendations above.

Dirty water, Grey water, Waste water

Often these are the byproducts of processes that started with clean water. The process will have added contaminants of one type or another, from particles through immiscible liquids like oil to chemicals.  Just what type of meter is suitable will depend on the level of contamination. Particles or bubbles: Doppler ultrasonic relies on particles or bubbles to bounce a signal off. It’s likely that measurement will still be possible using electromagnetic devices. Particles: Too much particulate can rule out transit time ultrasonic. Bubbles: Slugs of air: Gas, oil and water:

Some negative advice: Doppler ultrasonic and electromag are rendered useless. Some PD meters struggle at these margins of lubricosity.

Contact us

Talk to us today about your water flow meter queries today. You can contact our team directly on 01296 670 200. Alternatively, you can email us, [email protected] and we will come back to you shortly.

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