Kalk won't settle out of the solution

[Anonymous]

I am somewhat new to mixing kalkwater. When I mix the solution using Seachem's Kalkwater mix (calcium hyroxide) with my RO/DI water, the water stays cloudy forever. If i mix the kalk with store bought "drinking water" it settles out within a few hours. If I use tap water (from my kitchen faucet) it also settles out within a few hours. It is only when I use the water from my RO/DI unit that I have a problem. The unit is a 6 stage RO/DI and it's about 10 month old. I changed the 1st stage sediment filter after 6 month, as recommended by the manufacturer. I am planning to change all of the filters as recommended.

My house has a "whole house" water softner up stream of the RO unit. The incoming water service to my house passes though the water softner. I don't know if this has any bearing on my problem. I just thought I would mention it.

What should I test for to help determine the problem with this RO/DI unit?

Thanks!

Louey

 

[randy holmes-farley]

There are lots of issues that impact settling of solids. The one that you may be seeing here is that solids settle out faster when larger, and that many mineral solids aggregate when put in water that has some salt in it (like your tap water) compared to pure water. Putting fine sand into a tank of freshwater and having it cloudy, then seeing it settle on adding salt is an example, and you may be seeing the same thing.

Also, a limewater container with the lid open may never appear settled because CO2 is entering at the top, diffusing some way into the liquid, and then precipitating as CaCO3 (at least this is my interpretation of what I see). I've seen this myself: it appears to be unsettled for days when covered solutions of the same material appear to have already settled.

Consequently, I would not assume that there is any problem witha the RO/DI.

If you want the material to settle before use, you can either add a little table salt and see if that helps, or try a different brand of Ca(OH)2 that may have larger particle size.

 

[Anonymous]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote

If you want the material to settle before use

So it doesn't really matter if it settles? If it doesn't matter, I'll go ahead and use it. I assumed that something was wrong because from everything I've read about limewater indicated that it should settle out and that the liquid between the percipitate on the bottom, and the scum on the top, should be clear.

I will try adding a little table salt also, just to see if it has an effect.

I ordered some Mrs. Wages pickling lime also that I will try.

Thank you for the response!

Louey

 

[randy holmes-farley]

"So it doesn't really matter if it settles? "

Well, yes it does matter. Some people, especially before CaCO3/CO2 reactors became widespread, dosed milky (unsettled) limewater to get more calcium and alkalinity into the tank.

I personally have never (intentionally) done that. There are two risks, IMO:

1. Impurities in the solid (and water) that would precipitate in the limewater and never make it to the tank will get delivered. Heavy metals, phosphate, arsenate, etc. are all possibilities.

2. If you put in too much solid at once, you risk causing a precipitation event where CaCO3 comes crashing out of solution, turning the tank white. I have done this a couple of times by accidently sending sludgy limewater into the tank.

 

[CraigBingman]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Louey:
<strong>I am somewhat new to mixing kalkwater. When I mix the solution using Seachem's Kalkwater mix (calcium hyroxide) with my RO/DI water, the water stays cloudy forever. If i mix the kalk with store bought "drinking water" it settles out within a few hours. If I use tap water (from my kitchen faucet) it also settles out within a few hours. It is only when I use the water from my RO/DI unit that I have a problem. The unit is a 6 stage RO/DI and it's about 10 month old. I changed the 1st stage sediment filter after 6 month, as recommended by the manufacturer. I am planning to change all of the filters as recommended.

My house has a "whole house" water softner up stream of the RO unit. The incoming water service to my house passes though the water softner. I don't know if this has any bearing on my problem. I just thought I would mention it.

What should I test for to help determine the problem with this RO/DI unit?

Thanks!

Louey</strong><hr></blockquote>

Louey,

When you use tap water, there is probably a fair amount of bicarbonate+carbonate present in the water. When you add calcium hydroxide to that solution, you make some largish particles of calcium carbonate. These settle rapidly and pull the rest of the fines down with them. So the presence of carbonate alkalinity in the water is a bit like having a flocculating agent present in the water. (There also might be a bit of residual flocculant in your tap water, which will accelerate the process further.)

When you add calcium hydroxide to pure water, you wind up with a bunch of micron-sized fine particles in the water that take a really long time to settle out.

Operationally, you can use the calcium hydroxide solution after a couple of hours of settling, whether or not the solution appears clear yet or not.

Craig

 

[Anonymous]

Thanks Craig and Randy.

I mixed a new batch yesterday and will leave it sit for a few more days to see if it will ever settle out. It looks the same now as when I first mixed it.

I wonder if changing all of the filters on the RO unit would help? It couldn't hurt, just a possible waste of money. And that is a part of this beloved hobby, now isn't it

.

Thanks again!

Louey

 

[CraigBingman]

...
I wonder if changing all of the filters on the RO unit would help? It couldn't hurt, just a possible waste of money. And that is a part of this beloved hobby, now isn't it

.
...

No, changing the filters on the RO unit won't improve limewater settling time. If anything, it will settle more slowly with cleaner input water.

Craig

 

[Anonymous]

Thanks Craig. I bought a TDS meter and my RO is still removing 96.5% of impuities, so I won't change the filters until it drops to about 95%.

I decided to go ahead and use the cloudy limewater even though you and Randy had differing opinions on whether or not I should. I've been using it to replace evaporated water for about a week. My tank looses about 1 gallon/day. The makeup water is dosed via a micro-jet pump and a float switch. So far I have not had any noticeable problems. Coraline algea growth is good. I use 2 tsp of kalk/gallon of RO water. I use this along with 35 ml of Bionic added daily to maintain calcium around 400-410ppm and alk around 3 - 3.1 meq/l. I use the calcium BI-carbonate Bionic because my tank's PH runs high. It usually peaks around 8.5 - 8.6 during the latter part of the photoperiod.

I'll post here again if I notice anything interesting or alarming.

Thanks!

Randy Lewis