Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: What is the outside diameter of the no-spill float that hangs off the bottom of the tank?  I want to make sure it will fit down inside my cooler...
Document: The bottom tank and the inside of your water cooler are the only actual water STORAGE areas. Consequently, until you figure out just how much water to add, you may be overfilling this unit. Overfilling means ALL excess water will go onto the floor! There are no guidelines at all on how much water to add to the upper holding tank. There is only a water level mark on the BOTTOM tank.
Does not fit all standard water coolers!!! We purchased the water cooler first and were shocked when we got our zero water filter and found it does not fit. It requires a minimum of 6inch diameter and depth at the splash guard and a removable bottle spike. Many water cooler units do not meet these criteria. Now we're stuck with a water cooler we don't want and have to return the filters. Customer service was friendly but completely unhelpful. These requirements are nowhere to be found in product description or website.
I have to say that this filters very well. We used to have a Pur cooler bottle, but that unit has been discontinued and when we lost a part (and the Pur support is horrible), we needed to replace the bottle. At first we had a really big issue with the filter overflowing. After some investigation I realized that our cooler had a plastic tube that was interfering with the float valve inside the ZeroWater bottle. Since that was fixed it works well, most of the time.
I think it was my fault for keeping the filters on so long without checking the meter and changing in a timely manner. I removed the bottle and looked inside the cooler reservoir and saw this really gross milky white slime. I think after the filters have outlived their life cycle, this slimy water.is what comes out. I take that back. The slime stayed in the cooler tank and the water was still clear coming out of the spout.
It would not fit our water cooler and they don't make it easy to return. They also charge you a return cost
Then, adding approximately 2 1/4 gallons will fill the bottom tank to the fill mark. Sound complicated? It's not, once you get used to it. A rug full of water next to the filter/cooler was all it took for me.
This product is great. If you're used to lifting those heavy 3-5 gallon water bottles this will definitely make you smile. Compared to the price of regular bottled water along with the gas and energy expended to get it, the filters for this are a better buy (especially if you get them from Amazon with a subscription). Filling this is a breeze. You just pull the white top off and pour the water in. It goes through the filters and into the bottom bottle then into your cooler.
i think i love it, but i clearly didn't read the dimensions right, and it is much too large for the space that i had planned on. i thought i was buying my friend's set up, which i had seen before, and now i think that she might have had only one filter in hers... i'm not sure, but this is much too large for the space i had, but fit great with the ceramic water crock, and the stand, and the water tastes great so far.
I cannot comment on how well these filters remove contaminents from the water because sadly I didn't get that far. This filter was a replacement for the first one I ordered. The first one was defective at the base where the float valve is connected. The screw thread was worn away and it would not seal. Amazon as usual were great and sent me a replacement within a few days. This one had a defective lid. It was warped and twisted and would NOT fit the upper chamber.
I refilled the tank and right away the water had a fishy smell. To shorten the story it ended up being the filters, no smell occurred until I ran water through the filters, and then wham fish stink. Anyway I don't know if I want to get new filters for this it seems cheaper to go fill a 5 gallon container at the grocery store.
Answer: The diameter of the round plastic piece that hangs under the unit is 3 inches. It isn't actually a float. It hangs down 4 inches from bottom of the bottom tank. The most important thing to know about this unit is that it's NOT atmospheric pressurized like the Pur filtration system. The top part isn't really a water tank, it's just a glorified funnel. All the water is stored in the bottom tank. You can and will overflow the bottom tank if you add too much water to the top unit. I have gotten into the habit of adding two gallons to the top as soon as the unit is out of water. You probably could add another half gallon if you needed it. But with two gallons the unit doesn't overflow onto the floor.