Dosing Kalk Through Auto Top-off

[craighuckins]

I am thinking of making a kalk bucket reactor for my top-off water, system is AM perc 120 so approx 100 gallons, not a heavy demand on calcium, though alk/calc levels drop consistently in balance by a surprising amount. I am using about 25 litres Ro for top-off in 7-10 days (dependant on ambient romm temp). Anyone got any advice for amount of kalk powder to put in bucket to start with? I am petrified of overdosing and having a precipitation event, or do you think that say 2.5 - 3 litres of kalk going in over a 24 hour period would not be sufficient to cause precipitation? Or should I run two seperate pumps off the float switch, with one reservoir pumping raw RO during the day, the other pumping kalk at night? With them set on timers I could alter the ratio of kalk to Ro...Hmmmm like that idea! I like the idea of a kalk reactor, but the lack of control gives me the willies ;) Any thoughts, comments or experience would be greatly appreciated.....regards, craig.

[danny]

Unfortunately there isn`t a ratio of Kalk to water that anyone can give that will be a "safe level". The problem is that due to it`s lack of solubility the best way to use kalk is to put plenty in to make as strong a solution as possible then add it slowly to the tank.
By using reduced powder levels you have no idea what you are adding without costantly testing the saturation.
Saying that a guide often given is 1 tsp per 5 litres (this should achieve saturation if really well mixed, but adding 10tsp may not give you a stonger solution.
I use the tsp to 5 litre sRO and shaking it in a bottle gives me about 35% saturation, this means I can use it for all my top up without problems so long as I add it slow enough.

[Glenn@home]

Craig

I realise this is a potential problem and without complence computer control can be a worry.

How i deal with the issue on my system is to basically limit the amount of kalk that can be added should the system fail.

I do this by using a peri pump drawing from a 23litre bucket of ro so if the system fails immediately after i have refilled it then i will add five gallons of kalk over a period of 21/2 hours (ish) and tweny minutes at 16ml per minute if ive worked it out right.

of course anytime after topping up the ro reservoir would mean less kalk could be added.

I have never asked anyone with the specialist knowledge to decide of this would be disasterous for my system but i may just go and put a question on rc chemistry forum to see what response i get.

Regarding of how you time the addtion of kalk this i feel is more to do with the demand rather than anything else.

If the demand is high then it may be that you need to run kalk 24/7 to keep up with it.

The only way to know is to suck it and see afaik.

HTH

Glenn

[simonh]

It will require around 1.5 - 2grams of calcium hyroxide per litre of RO water to make fully saturated limewater. However, you may not need fully saturated limewater to keep up with your calcium / alkalinity demands and so may wish to start off at a lower amount and see how it goes. Often the other limiting factor is how high your daytime pH gets which can often be overcome by dosing just at night rather than throughout the day.

I personally would recommend a variable speed dosing pump that you can dial in so it just doses the amount of evaporation each day, this was your system will be far more failsafe should a floatswitch get stuck... and it also works well if you want to combine a timer for dosing only at night with the floatswitch.

[Glenn@home]

Simon

Not saying it cant work, but rather pointing out some of the potential problems with a 'dialed in peri pump' approach.

I find the evap on my tank varies with the weather quite a lot.

As much as I would hate to o.d. the tank on kalk this is a potential problem whihc may never arise and in my case the evap issue is a real problem.

For me and anyone else whos evap varies an auto top off device possibly combined with a kalk stirrer is the way to go.


JMHO

GLenn

PS i have posted a question on rc chemistry forum re the potential for fatal kalk overdose and how vulnerable we are.

[simonh]

Glenn,

I'm not sure there is any dissagreement between us. I was suggesting a dialed in peri-pump that could be combined with a floatswitch if required. Which would make a very failsafe system.

[Glenn@home]

Simon

Thanks for that i didnt read it that way, no problem

FWIW i made a post on rc and Randy is giving some views, hopefuilly he will give us a good idea about the actual scale of the problem.

Glenn

[Glenn@home]

Hi all

Have just had an exchange of info with randy (http://reefcentral.com/forums/showthread.php?s=&postid=4832153#post4832153)

basically it seems if you limit the amount of kalk that can accidentally be dosed to your tank to around 1.25% of the system volume then it seems unlikley that the o.d. will kill stuff.

There are so many variables from system to system that it is unliklely that any guarantees can be given one way or the other.

Practically 1.25% of my system would be just about workable based on my average evapouration rates, but in the summer might be a problem.

Randy does make the point that he cannot be certain at what point an overdose goes from a simple snow storm event into something catastrophic but he feels that most overdose events are simply snow storms which are effectively self limiting in terms of raising pH and kalk/ca levels.

So for me i would have to bank on the ro bucket being only a third full if and when i had a fault with the top up system to be safee (ish).

I guess we can all make our own minds up which way we go, I have had problems with my float switch sticking, but usually in the off positio in my case, and my peri pump has stuck too, the effect of this is to reduce the addition rather than increase it whihc of course is still undesireable but safer.

My float switch i got from jackok in a swap and it works well and is designed to redcue the chances of getting stuck, to me this coujpled with the limiting of the amount of kalk that can be added is reasonable.

JMHO

Glenn

[craighuckins]

Well thanks for all the thoughts and info - have had the bucket reactor running for a few days now and levels seem to be stabilising nicely- DKH 8.7 and calc. 420ppm which is as near as damn it in balance so I'm happy :thumbsup:

[Dursley93]

Hi all

I am planing to use a ph controller with solenoid valve placed off a tee between peri pump and kalk stirer. When the ph hits a predetermind level the valve will open and the fresh ro takes the easy route direct to the sump

Phil :wacko:

[Adam C]

I dose kalk with a peri pump conected to a auto topup via a plugin segment timer (not a digital one). The dial on these only turns when there is power, so if say you want to limit the max amount of kalk in a day to 5 litres and your peri pump supplies 1 litre a hour you set the timer to be on for 5 hours. This does however mean you have to reset the dial on the timer once a day.