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Andysworld! Advent Calendar - Dec 20 - Andy needs another TDS Meter - dropped mine in a bucket of water!

Looks like I’m going to have to purchase a new TDS meter, I dropped my current TDS meter, in a bucket of reverse osmosis water, and I now know, it’s not waterproof because it’s stopped working! (if you cannot be bothered with all the text, just scroll down and watch the video!)

So the last sentence is probably reading gibberish for the non-fishkeepers or chemists among you, TDS - Total Dissovled Solids - many different definitions, but in simple terms a measure of the combined content of all inorganic and organic substances contained in a liquid.I live in a very hard water area, it’s like liquid rock coming out of the tap, pH is very high, approx 8.5 (alkaline) - that stuff that furs up the kettle, washing machine and dishwasher elements - is the calcium carbonate (chalk) - it just so happens that the Yorkshire Wolds are very chalky, so the water that flows through the chalky hills, ends up with chalk dissolved in it! (different to when we lived on near Dartmoor, the water was acidic, because the water runs off the peaty moors!). So TDS of my tap water is approximately 490.

Problem, I keep many fish from South America, which prefer acidic water conditions, of a pH of approx 6.0 - 7.0 (neutral). Put them in declorinated, mature water of 8.5, and they are not going to be very happy or breed.

The TDS meter allows me to check, the water quality output after it has been “treated” from, the Reverse Osmosis units, it’s not really “treated”, Reverse osmosis (RO) is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be “selective,” this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as the solvent) to pass freely.

So the water which is output from the RO units, is very pure, with very little inorganic and organic substances, TDS reading of 000 - 001 is obtained. This is almost the equivillent of distilled water, which is used to top batteries in cars, and also used in your iron, to stop it furring up (remember that chalk again!).

RO water it is too pure to sustain proper chemistry to support an aquarium ecosystem, so I re-mineralised with the correct aquarium salts, or blended with existing filtered tap water.

Here’s a quick video, of my Commercial Laboratory quality ELGA Reverse Osmosis Units, in the fish house:-

Apart from the following video, maybe giving you a headache, because of the microphone on the video camera, picks-up the pump noise (it’s not that loud in reality), the noise of running water may want to make you go to the the toilet!

Water is fed through the following stages

  • STAGE 1  - 5 micron Sediment 10″ filter made of 100% pure polypropylene fibres. removes dirt, sand and rust
  • STAGE 2  - 1 micron Sediment 10″ filter made of 100% pure polypropylene fibres. removes dirt, sand and rust
  • STAGE 3 - a granular activated Carbon 10″ filter composed of high - performance activated carbon. removes free chlorine, odour, organic contaminants, pesticides and chemicals.
  • STAGE 4 - a carbon block 10″ filter composed of high performance carbon. removes trihalomethanes, pesticides, volatile organic chemicals and 99.95% of giardia and cryptosporidium cysts
  • STAGE 5 - A ChlorPlus-10 10″ filter designed to remove chlroine and chloramines.

(it is important, as the reverse osmosis membrances are expensive, not to clog them up, or damage them with chlroine.

  • STAGE 6 - Water is fed into the Elga Boost Pump, which has a small water filter (STAGE 7) before water is fed into a small water tank, maintained by a float system, so water is pumped from this tank under pressure. The pressure is approx 8.5 bar, which is double tap water pressure.
  • STAGE 8 - Water is then fed into a Elga Prima 1, which has another pretreatment cartridge (STAGE 9) which protects the RO membranes by removing particulates and chlorine. This unit has two RO membranes. (STAGE 10 & 11)
  • STAGE 12 - Water leaving the  Elga Prima 1, is then fed into a Elga Prima 3, which has another pretreatment cartridge (STAGE 13) which protects the RO membranes by removing particulates and chlorine. This unit has 4 RO membranes. (STAGE 14-16).

Water leaving the Elga Prima 3 has a TDS of approx 0.

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