Big Berkey® 8.5L

Yes, it is entirely normal for 1 to 2.5 cm of water to remain in the upper and lower chambers. For water to be filtered, it must pass through very fine micropores in the filters. The lower the water level in the upper chamber, the lower the pressure available to force the water through the micropores. You may have noticed that the filtration rate is much faster when the upper chamber is full than when it is half empty. This is because there is more pressure. The only way to remedy this would be to enlarge the pores of the filter elements, which would reduce the effectiveness of the Berkey purification system. During each cycle, the residual water from the previous cycle mixes with the water from the current cycle and is then purified. Therefore, there is no need to worry about the excess water during normal use. However, if you stop using your filter for an extended period, such as during a vacation, it is best to empty both chambers and let them dry completely.

Regarding the lower chamber, the spigot cannot technically be positioned at the bottom of the tank for sealing reasons. Don't worry; this is not stagnant water as it will mix again and again during successive filtrations.

The following response applies to all models in the Berkey® range, with adjustments for volume calculations.

The volume of each model refers to the volume of the lower tank. This means you can have up to 8.5 liters of filtered water in stock.

Explanation: The upper tank is slightly less voluminous for safety reasons to prevent overflow if the lower tank is not completely empty.

To be more precise, for the Big Berkey, the top tank has a volume of 8.32 liters. Additionally, the volume of the Black Berkey® filters must be taken into consideration. Each filter has a volume of 0.51 liters.

If your Big Berkey is fitted with 2 filters, you can fill a maximum of 7.3 liters of water.

You will actually fill slightly less than this because there is always about 2 cm of water remaining at the bottom of the tank (see explanation here).

Also, when you have emptied the lower tank, roughly 1 liter of water will still left in the bottom of the tank (see the previous link).

The amount of water you can put in the upper tank has been carefully designed and determined by the manufacturer to allow, in regular use, a volume of 8.5 liters of filtered water in the lower tank, whilst preventing a risk of overflow.

Tip: If you would like to completely empty the bottom tank into a jug, this can be done by tilting your Berkey® forward gripping the knob on the lid.