Yep another RO/GH question

[dragon1974]

Ok so lastnight I'm redoing my fish area (can't really call it a fish room as it's only one rack LOL) and decided to use the reject water from my RO system for my grow out tanks. Long story short, I did a reading on both my RO barrel and reject barrel and my KH reading was 3 drops 0-50 PPM but my GH was going well over 30 drops.

Question, how is that even possible LOL or am I missing something? My RO barrel isn't being areated but my reject water is being aerated. Any Idea why this is happening?

[pcsb23]

I'm sure the question makes sense to you, but it doesn't to me ...

Which barrel has what readings?

[nc0gnet0]

What is the reading of your tap water? sounds to me like your RO membrane is failing. Your RO water should be dam close to 0 on both KH and GH.

[dragon1974]

I'm sure the question makes sense to you, but it doesn't to me ...

Which barrel has what readings?

Actually both barrels are giving that reading.

[dragon1974]

What is the reading of your tap water? sounds to me like your RO membrane is failing. Your RO water should be dam close to 0 on both KH and GH.

That was what I was thinking. Might have to get a replacement soon.

[dragon1974]

I let the water sit for a couple days so I'm going to do another test later

[dragon1974]

I'm sure the question makes sense to you, but it doesn't to me ...

Which barrel has what readings?

Sorry man, yep I'm really sure that the question made sense to me LOL. The question was, if my KH is reading so low, how come my GH is reading so high? Shouldn't they both read the same or even close to the same? I was hoping the membrane wasn't failing but after my reading tonight I would decide if to replace or not.

[pcsb23]

OK, if both barrels are giving the same reading it does suggest your membrane is shot, sorry.

You wouldn't necessarily get the same or similar kh and gh readings as they depend on the type of mineral content in your water.

KH is a measure of carbonates and bicarbonates, these affect the pH and the water's buffering capacity.

GH measures the total concentration of mainly calcium and magnesium ions in the water, other so called metals will have a small impact.

So as an example, if you added Epsom salts to your water the gh would increase but the kh wouldn't - this is explained because Epsom salts has the formula MgSO4 - i.e. no carbonates/bicarbonates, but does have magnesium (Mg). If you added sodium bicarbonate your kh would increase and there would be an increase in GH too - in this case sodium bicarbonate has the formula NaHCO3 - the sodium (Na), being a metal will contribute to the GH, the bicarb to the KH.

If your water is hard, and the minerals that make up that hardness are mainly in the sulphate/chloride/chlorate type forms then you will get low kh readings and high gh readings.

I'd definitely be testing your tap water though as that is the source, that may clarify things a bit.

[nc0gnet0]

I'd definitely be testing your tap water though as that is the source, that may clarify things a bit.

+1

Another thing I might add, a water softener will significantly lower GH, but have no effect on KH.

-Rick

[dragon1974]

Yep guys,

Tested my tap and both KH and GH are over 20 drops with no change to water colour. No watersoftener yet but I'm going to have a bypass so that I get straight tap water for the fish. I'm going to look into another membrane as this system is more than 5 yrs old

[pcsb23]

Make sure you change out the carbon filter too, if chlorine gets to the membrane it will ruin it.

[dragon1974]

I changed the carbon a month ago, but it was really dirty so maybe I might have to clean it again and test.

[dragon1974]

OK so I changes out the membrane and added a couple new filters (5 micron + 1 micron). The carbon was changed a couple months ago and was not used that much. Anyway I also added a dual TDS meter when tested both incoming and outgoing water. Readings incoming were around 290/300 ppm and my outgoing reading was 45/50 ppm. I guess I needed to change everything. I'm going to test the water in the barrels tonight so we'll see what the drop counts say. Will post the results later tonight

[pcsb23]

OK so I changes out the membrane and added a couple new filters (5 micron + 1 micron). The carbon was changed a couple months ago and was not used that much. Anyway I also added a dual TDS meter when tested both incoming and outgoing water. Readings incoming were around 290/300 ppm and my outgoing reading was 45/50 ppm. I guess I needed to change everything. I'm going to test the water in the barrels tonight so we'll see what the drop counts say. Will post the results later tonight

Still doesn't sound right, sorry to say.

My water has similar properties in terms of TDS, over 300 incoming, pH around 8.2 and fairly cold even in summer! The product water is between 5 and 7. That is what you should be getting too, either water is getting around the membrane or the membrane is shot.

[dragon1974]

Interesting....Not sure then what to do. My RO is a standard system and the membrane fits like a glove in the holder. I'll have to check again and make sure that everything is in working order.