Approximately 9.5" Dia. X 10" Ht. (2.5 Gal Capacity)

THE GE MERLIN REVERSE OSMOSIS FLUSH KIT...DO YOU NEED ONE?

One of the performance characteristics of all Reverse Osmosis (RO) systems is their ability to reduce Total Dissolved Solids (TDS) from feed water. TDS is a measure of dissolved ions in water and is a good general purpose indicator for determining water purity. Higher TDS readings indicate more dissolved minerals or salts are present in the water.

When they are producing water, all reverse osmosis membranes operate with two sides of water production, a high pressure, high TDS, waste water side, and a low pressure, low TDS, RO water side. The high pressure, high TDS waste water production is typically sent to drain or stored for other non critical uses. The low pressure RO water production is what is consumed usually. This high and low pressure operational characteristic causes an imbalance of hydraulic pressures across the membrane surface to achieve what is known as reverse osmosis. As long as the RO system is producing water and the forced pressure is being continuously applied, this reverse osmosis process will continue with the high TDS water flushing rapidly from the one side of the membrane and the RO water being produced slowly on the other side of the membrane.

When the process is suddenly stopped by un-applying the feed pressure, such as when the faucet is closed on the Merlin system, the imbalance of hydraulic pressure still exists across the membrane surface as described above. As time passes and the the membrane sits idle, the high TDS concentration on the high pressure waste water side of the membrane will slowly begin to "creep" into the low pressure RO water side of the membrane, as the natural "osmotic" process takes over.

As a result of this TDS creep, when you turn the system back on, the initial RO water at system start-up will contain a temporary spike in TDS. This means that the water that comes from the faucet initially, after the system has been sitting idle for a period of time, is often much less representative than the true pure water quality that the RO membrane is capable of producing vs. if it had been running continuously for a period of time.

There are two ways of dealing with this TDS spike. You can flush the system manually by leaving the faucet or point of use open and letting the system run for a few minutes or you can install a Flush Kit that does it automatically so you will have instant RO quality water every time the faucet or point of use is opened.

The Merlin Flush Tank helps prevent the effects of TDS Creep by automatically flushing the system after each and every use.

HOW THE FLUSH TANK WORKS

A series of check valves within the Merlin's manifold automatically redirects several gallons of RO quality water into the flush tank immediately after the faucet or other point of use is shut off. Once the pressurized flush tank is full with RO quality water, it then automatically forces the RO water across the membrane, which in turn flushes the high TDS water from the membrane. Now that the membrane has RO quality water on either side of it, (equal pressures), the effects of TDS creep or salt diffusion are virtually eliminated.

For proper operation, the tank holds an air precharge of 8 to 10 psi. An 8 liter tank is the recommended size for installations with feed water containing 750 mg/L TDS or less. Installations with inlet water containing more than 750 mg/L TDS may require a larger flush tank. A Larger tank, in this situation, will create a more complete system flush and will therefore allow even less TDS passage.

Simply put, a flush kit allows the user to alleviate the effects of salt diffusion resulting in immediate RO quality water when the system is turned back on after periods of inactivity.

WHO NEEDS THE FLUSH TANK?

This Flush Kit is recommended for applications where a spike of TDS at system start-up is not desirable, such as in a commercial setting where initial high purity water is critical. In this type of setting, the flush tank is an effective way to maintain consistent high water quality with each opening of the point of use.

We also recommended this Flush Kit in residential settings where significantly high TDS >750 mg/L are present in the feed water.

One obvious downside to the flush tank installation is that many people purchase the Merlin simply because of it's touted "tankless" feature which saves room for installation.

Another not so obvious, at first glance, downside is that the flush tank wastes a lot of water. This is because the flush tank will fill and flush the membranes each and every time the Merlin's faucet is opened and closed, regardless of the amount of water that is taken for consumption. The system flush occurs after each and every demand for product water, whether large or small.

With this Flush Tank installed on the Merlin, the user should expect the Merlin to run for an additional 5-8 minutes after the faucet is turned off and also expect to waste an additional 3-5 gallons of feed water to drain each and every time the faucet is turned on and off.

IN CONCLUSION:

For the average residential and commercial settings the Merlin without the flush tank will be sufficient. We recommend just simply running the product water to drain for 1-3 minutes after the system has been sitting idle for a period of time, say overnight or after a day or so of non-use.. This method will produce almost the same results as having the flush tank installation, and waste a lot less water over the long run. However, there are cases, such as homes that are on well water with very high TDS concentrations, and commercial settings that require high purity, where the flush kit would be a beneficial addition.

The Flush Tank kit includes a pre-charged RO storage tank, a base to hold the tank upright, tubing, and a tank valve fitting. The tubing and tank are connected to the light blue 1/4-inch elbow connections on the Merlins' manifold.