House water filters

Whole house water filters caused lots of troubles to planted aquarium enthusiasts in recent years. The reason is the hidden principle most of these filters work on. These systems are regenerated with sodium chloride NaCl or potassium chloride KCl, so when calcium Ca, magnesium Mg and other cations flow through such systems they are filtered out and replaced with the same quantity of sodium Na or potassium K. The produced water reads zero GH because the GH elements are stripped away. Instead, there is a high level of sodium Na or potassium K that can be tested by highly elevated TDS readings.

FAQ

Why my water have high pH, high TDS and low GH?

If the chemical used to recharge the house softener is sodium chloride NaCl then Ca and Mg are replaced by sodium Na. If potassium chloride KCl is used then Ca and Mg are replaced by potassium K. This sodium or potassium form sodium carbonate Na2CO3 or potassium bicarbonate KHCO3, which are alkaline pH buffers.

Basically, the water out of the softener is water

• with no Ca

• with no Mg

• with added Na or K

• with added alkaline pH buffer

Ca and Mg need to be added back in, in form other than CaCO3 and MgCO3 because they increase KH. This water doesn’t need more KH. Also other than CaCl2 and MgCl2 because there is already Cl leaked from the NaCl or KCl regeneration chemical procedure. CaSO4 and MgSO4 can be used, also CaNO3 and MgNO3 if more NO3 is needed.

Higher the GH before filtration, higher Na or K and pH after filtration.

Can I use such water for my planted aquarium?

Only if you are planning to grow other than soft-water low-KH difficult species.

So how can I fix it?

Tap the water line before the whole house filter and grow hard water plants. Or, tap the water line before the house filter, install RO reverse osmosis unit, and add Ca with Mg .

What if my water have high pH, high TDS and low GH before the whole house filter?

That means that the water was processed in such way by the water utility. Your option is to grow hard water plants, or install RO reverse osmosis unit. In either case you will need to add Ca with Mg as per Plant requirements.