Which Ro

[Marc025]

Hi all, I have a Merlin RO at the mo which is on its last legs. PPM are getting higher and higher, filters need changing. So using this as an excuse to replace.

My question is what's the difference between the 40/40 and 40/21 RO and would I be better if with 2 pre filters or 3, may thanks in advance..

Marc

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[spruce]

Hi all, I have a Merlin RO at the mo which is on its last legs. PPM are getting higher and higher, filters need changing. So using this as an excuse to replace.My question is what's the difference between the 40/40 and 40/21 RO and would I be better if with 2 pre filters or 3, may thanks in advance..

Marc

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A 4021 is half the size of a 4040 so will produce less water over the same time span.

A 4021 is more than adequate for all single operators, but if your intention is to grow then I would look seriously at a 4040. A 4021 can be upgraded to a 4040 spec by adding another housing and membrane, but further down the line replacing 2 x 4021 membranes is more expensive that 1 x 4040 membrane.

A 4040 is a much longer r/o so space might also have an input into your decision.

You will also need to provide an automatic cutoff system when your storage tank is full. Gardiners and Purefreedom sell these kits. The Merlin is good for this as you just use a float valve in the tank. Once the pure is shutoff the r/o stops.

You only need a maximum of 2 prefilters for window cleaning. I would recommend using 20" as the filters last longer. We use both a sediment and a carbon block prefilter in separate housings. Our water at times is sediment laden so we use a separate sediment prefilter to protect the carbon block. (Another local cleaner has an old Merlin and he has fitted a single sediment prefilter before his r/o for the same reason.) We use Fiberdyne carbon block filters from Gardiners. They can also be used as a prefilter as the Merlin units do, so in that case you only need one prefilter.

What I like about the 4021/4040 units is that membranes can be ordered to suit your water pressure. HF5 for low WP and HF4 for higher WP. Our WP is 50psi and we get good performance using an HF5 membrane. Our unit produces about 2 liters of pure per minute without a booster pump. (99 to 125ppm tap water tds input, 2ppm output.)

4021/4040 aren't as water hungry as the older Merlins so you will use less water. They are also much more efficient so you will use less resin 'polishing' the water off.

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