Using dosing pump for topoff

[dieselkeeper]

My 10 year old diy top off got salt creep inside the box and into the relay. Everything has green corrosion in it. I have a dosing pump that I'm not using at the moment. I'm looking to use it without any float switches. Is it possible to get a daily dosing of RO water consistently for topoff?

 

[DLHDesign]

I wouldn't consider it to be a safe option to use a pump for an ATO without some kind of emergency kill-switch (generally a float switch, but also optical sensors fit the bill).

You could (in theory) measure your average daily evaporation and set the dosing pump to return this amount into the tank. The problem there is that you are unlikely to have a perfectly consistent evaporation rate, so some days you would dose in more than needed, and some less - which means you have instability in your salinity. Likely not much of one, but some.
You would also be risking a tank overflow should the dosing pump fail in the "on" position. You could mitigate this by keeping your source container small enough that such a failure would not overflow the tank, but then you would likely have to refill it quite frequently - which kind of defeats the purpose of an ATO...

 

[bif24701]

I find using my APEX to add a specific amount of Kalk every 1/2 hour has been more than consistent, it’s practically flawless.

My system is a 32 Brute store my Kalk. 50ml/min BRS ATO pump/doser controlled via my APEX. It is set to run for 5min every 1/2 hour. I’ve been using this for 3 years and by far the most reliable ATO system I have use and/or could possibly conceive.

The evaporation rates are almost predetermined by surface area. Weather and humidity can affect it however since your system is indoors (assuming) that variable is very very small. The conditions indoors is consistent enough that there will not be any considerable drift of salinity.

Sensors fail. I don’t use them, not needed. You can actually calculate the evaproation rate and determine how long the pump needs to run to make up for it. Set up a timer for the pump. And observe for a few days in the beginning. Make any adjustments if you do notice a drift but make them tiny. Observe for a few more days. I’ve not had to adjust the timer on my pump in the entire 3 years due to a drift in salinity. Since I use Kalk I have had to slow it down a little because ALK would creep up but that’s a totally separate issue. If you are using fresh water only that’s not a problem.

This is though the best implementation of Kalk period. Slow and steady and no risk of over dosing.

Good luck