First-Time Reverse Osmosis Startup: Air Purging, Flushing, and Cloudy Water

Cloudy, milky water or a sputtering, uneven stream from the faucet immediately after first starting the Hydrion Purity RO600 or replacing a filter is almost always caused by air trapped in the tubing and the new filter, not a fault. The system manual itself instructs you to run water for twenty minutes after connecting the tubing and power, before filling the first glass for drinking, and switching on the power also automatically starts the membrane flush. Below, we explain what causes the cloudiness, provide a simple glass test to distinguish normal air purging from a real problem, and tell you plainly what the manufacturer does not specify after a filter replacement.

• First startup: run the faucet for twenty minutes before trusting the first glass.
• Cloudiness caused by air usually clears from the bottom of the glass upward within half a minute to two minutes.
• After a filter replacement, the manufacturer does not specify a separate flushing time, so it is better to rely on the glass test than to assume the same limit as for the initial installation applies.
• The first TDS reading after an extended period of inactivity can also be temporarily higher. This is a separate, normal feature of every reverse osmosis system and is unrelated to cloudy water.

What the RO600 manual itself says about the first day

The RO600 installation manual is unusually specific in the step labeled “Plug In And Flush”: after connecting the tubing and power, you need to run water from the faucet for twenty minutes before filling the first glass. This is not a general precaution added just in case, but a step explicitly included in the initial startup process.

At the same time as you switch on the power, the system automatically starts flushing the membrane. This is not a separate task to perform manually, but part of the same initial operating cycle. The membrane is flushed automatically every time the power is switched on, after the unit has been in use for an extended period, and every twenty-four hours while the system is in standby mode. The RO600 itself stops after thirty minutes of continuous operation as a safety measure.

It is worth remembering that these twenty minutes are specified for the initial installation. The product page does not give a corresponding number of minutes for every subsequent filter replacement, a distinction we return to below.

Why new filters and tubing release cloudy or sputtering water

Opening a factory-sealed filter and connecting tubing that was previously dry introduces air into the system. Under the pressure inside the system, this air remains dissolved in the water until it reaches the open faucet, where the pressure drops sharply and the gas separates out as tiny bubbles that look like a milky haze from a distance. A sputtering or uneven stream when the faucet is first opened is usually the same pocket of air moving through the tubing, not a sign of a leak.

Colder water from the mains dissolves more gas than warmer water, so with colder tap water in winter, this phenomenon is sometimes a little more noticeable than in summer (source: Frizzlife - Reverse Osmosis Cloudy Water: Causes & Fixes). Because the RO600 has no tank, purging the air simply means running the faucet continuously, rather than filling and draining a tank several times. This is different from the approach in many general guides to reverse osmosis, which describe the same process in terms of tank cycles.

The glass test: how to tell air from a real problem

Pour water straight from the RO600 faucet into a clear glass and set it aside without moving it again. Cloudiness caused by air visibly clears from the bottom upward, usually within half a minute to two minutes: you can see a clear boundary between the layer that has already cleared at the bottom and the still-cloudy layer above, which gradually disappears.

If the cloudiness has not cleared after about ten minutes, or you can see particles settling in the glass, discoloration, or an odor, treat it as something other than air still escaping from the water. That is a reason to check the installation, not to wait for another glass.

What a filter replacement resets—and what it doesn’t

The RO600 filter replacement process is described as removing the front cover and turning the old filter. The manufacturer says the whole process takes about three seconds and requires no tools. What the product page does not specify is a separate flushing time for this particular replacement, unlike the twenty minutes specified for the initial installation.

The most honest approach, then, is not to assume that the same twenty minutes automatically apply to every subsequent replacement, but to use the glass test described above: run the water until the cloudiness clears on its own as described. Since most replacements are made with the power on, the same automatic membrane flush mentioned above also helps rinse the newly replaced filter.

If you have questions after replacement about the installation itself—for example, whether the three-way valve or the 1/2-to-3/8-inch adapter is connected correctly—the manufacturer offers to check a photo of the under-sink installation by email. For a complete, step-by-step description of the filter replacement process itself, see the separate guide: how to replace filters and the membrane in a reverse osmosis system.

Why the TDS reading can also jump at first

The manufacturer’s own FAQ notes that the first water reading after the system has been idle for an extended period may show a slightly higher TDS value for about a minute, and describes this as a normal phenomenon for every reverse osmosis system, not just the RO600.

This is separate from the cloudiness described above. A higher reading on the display during the first minute does not in itself mean the water is unsafe or that the membrane needs attention. If you want to know what TDS level is normal in everyday use and what a sustained increase means, that is covered in a separate guide: normal TDS levels in reverse osmosis water.

When to check the installation instead of waiting

Cloudiness that persists long after the glass test, especially if it returns over the next few uses, no longer looks like a one-time release of air. Particles settling on the bottom, discoloration, a persistent odor, or a flow rate that is noticeably slower than usual are reasons to check the supply valve and connections instead of waiting for another glass.

Start with the included three-way valve and the 1/2-to-3/8-inch adapter, as these are the main connection points in the RO600 installation and the easiest to check yourself. If the problem is not simply air purging, you can find a broader overview of common faults and what to check first in the separate guide: common problems with reverse osmosis systems. If, on the other hand, cloudy water comes from an ordinary mains-fed faucet in your home, unrelated to any reverse osmosis system, that is a different topic, covered here: why tap water can be cloudy.

If the glass test confirms that it is just air from the initial startup or a freshly replaced filter, a natural next step is to compare your own under-sink installation with the Hydrion Purity RO600 setup, especially the supply valve and adapter, to make sure everything is connected as the manufacturer intended. For a broader overview of reverse osmosis technology, including how the individual filtration stages work, see the complete guide to reverse osmosis.