Water level sensing and pump

I'm brainstorming the best way to approach my next project and could use some input.

I have a water filter tank that's about 1.25 gallons that holds the water as it filters. Then a holding tank that's about 3 gallons.

I simply want to turn on a 12v pump when the water drops to a certain level in the holding tank in order to refill it.

The only complication is that the filter tank is smaller than the holding tank so I may need it to do two cycles of refills in order to get the tank level refilled.

My idea is to have two float switches in the holding tank - one at the bottom and one at the top. One to tell me when it's empty and one to tell me when it's full. Then one float switch in the filter tank so I don't overfill it.

I also saw some water level sensors on eBay. Anyone have experience with those?

Some years back I built a pond filtration system for my brother. The issue is that, even with the information that your reservoir is lacking water, you have no way of knowing how much is still on it's way from the filter. So you could easily overfill.

The answer is to have the draw from the filter at the top. As it fills from the bottom and rises through the different filtration layers it spills out of an overflow pipe into the main reservoir. If you stop the pump at any time it immediately (or almost) stops spilling out so problem solved.

You still need to have a level switch in the filter in case it's outlet gets blocked.

my issue with drawing from the top is that it is a gravity fed filter. The pump would just be filling the tank. It's a tank with two filters screwed to the bottom. The water seeps through the elements and drips out the bottom.

if you have hi and low in the filter, and know the volume it takes between, then all you need is a low on the tank.

pretty simple. and fool proof. knows when to fill the filter and can never overflow.

if you add one at 3/4 for the tank and one at half for the filter, you can add more to the tank.

next comes the water flow sensor. with that, you can add as you need.

How about one float switch in your holding tank that is 1.25 gallons from the top. If this turns off the pump, then even if the filter is full, it's not going to overflow.

As soon as the level drops below this, it's safe to turn on the pump again. In the meantime you can have a separate float switch in the filter. This could even be run in series with the float switch in the holding tank.

Hi, how do you control the flow from holding to filter tank. Can you draw and post a diagram of how your tanks are arranged and fed.

Tom....... :)

Here’s my rough idea - maybe I’m making it to complex… I just don’t want to end up with endless water pouring into the kitchen…

The two rectangles in the filter tank are the filters attached to hoses.

The system would be activated once Float Switch Circle is closed by low water. The pump would turn on and fill the filter tank until it closes Float Switch Triagle. Then it would wait a designated amount of time for the water to filter in and then fill the filter tank again. This would happen until Float Switch Square is closed by the filled holding tank.

Anyone seeing any puddles this way? A better way?

I also have a flow meter that could be stuck in there somewhere…

How about a float VALVE in the holding tank then you only need a float switch in the filter tank.