Photo of the prefilters.
Photo of the water softener.
Photo of the RO unit.
Using Reverse Osmosis to improve supply water quality.
I run an RO plant and I can assure you it’s not rocket science.
I’ll explain my system and method of mixing water to a totally safe level.
My RO plant produces 2 ½ litres of RO water per minute, it’s a commercial unit with two 4’ membranes and a ¾ horse motor pressurises the unit and forces rejected water through the second membrane, thus saving waste water. This is not an under sink model, as these would not produce anything like the amount of water I am looking for to feed a couple of small ponds, or one larger.
The layout is so: main tap water is first fed to a double canister 5 micron prefilter, followed by a double canister carbon filter. These are the same units you would use to remove chlorine from your tap water for pond use. These are firstly fitted to remove chlorine prior to the RO unit, as chlorine has a damaging affect on the membranes and also it is tee’d off to later be used as my mix water.
Next in line is a domestic water softener. This is used to soften the water fed to the RO unit, otherwise the membrane quickly becomes coated in limescale and the output of product water would decline. This then feeds onto the RO plant.
My mains city tap water has an average reading of KH18, GH 22, PH 8 and TDS 380. The readings coming from the carbon filter are very similar, with little change. This is far to high for my comfort, but I use this water, mixed with RO water to achieve the water chemistry I am after. I do not run dangerously low levels; I leave myself a little buffer room.
On the side of the pond I have two taps, sometimes I let these run continuously, other times just over night, depending if the pond readings are as I would like.
Out of one tap comes RO water; out of the other comes carbon-purified tap water. To ensure the water entering the pond is of a level I am happy with, I hold a glass under the two taps combined, this is a mix of water. I then test the KH and TDS. I wish the pond to run with a constant KH 3, to keep this level with my summer heavy stocking/heavy feed I add new water with a reading of KH 5
Out of one tap comes KH18, out of the other comes KH 0. The taps are adjusted to give this mix, more RO water than mains.
This new water has a TDS reading of 80ppm and the pond runs at TDS 90 to 100ppm. After a while it is possible to judge the KH of the feed water and pond water by the TDS level and withhold KH testing, for example I know my mix of water at TDS 80 will be a KH 5, with very little fluctuation. I test KH every few days for reassurance.
Since installing my RO plant (it was not only installed to reduce KH, GH, PH and TDS, but also to remove elevated copper levels in my mains water) I have reduced standard pond readings of KH 18, GH22, PH 7.8 and TDS 440 to KH3, GH5, PH 7 and TDS 90.
I have meters giving constant PH and TDS readings, plus I use a dip TDS meter to monitor new water.
While I go to Japan, my wife Lynn runs the whole show with no problems. The worst thing that could happen is the RO plant could break down; all that would result in is a climbing KH, as the mains water would continue to run. No chance of a crash.
Photo of the prefilters.
Photo of the water softener.
Photo of the RO unit.