Why filter wine if it will clear on its own? A clear wine is more appealing, the color is brighter. Filtering may make a wine drinkable sooner. A sterile or fine wine filter will remove most yeasts that may cause sediment and possibly refermentation. The disadvantage of filtering is the possible reduction of color and tannins. These are reasons why I don't filter red grape wines, but quickly filter fruit or country wine and white grape wines.
There are several types of filters available, ranging from an inexpensive gravity feed to fully closed pressurized multiple plate filter system. This system is used by high volume wineries. A big disadvantage of gravity feed is the introduction of oxygen and bacteria. The closed pressure system eliminates the oxygen contact, but it is far too costly for most home winemakers. The home winemaker needs something between the two filters. I have designed a filter system that is motor driven, low priced, and is easy for the handyman to build in a couple hours.
If you build this wine filter, read and understand all instructions before going to the store to buy parts. First thing needed is a self priming pump. Self priming does two things, it will draw the wine into the pump without needing to manually siphon it, and will create a better pump output pressure. A small motorized pump is available from many fleet stores, or better hardware stores. I used a SIMER #M40 that will pump about 360 gallons per hour, on sale for about $60.00. The bad part of this pump is that the pump instructions tells you to oil the pump before using. DO NOT oil this pump. While running liquid through this pump, lubrication is not a problem. If you do need to lubricate the pump, you may consider opening the pump and using some glycerin or a small amount of vegetable oil to lubricate. If you can find a pump system that is rated food grade and can deliver about 25-40 psi, that would be better.
For the filter housing I used a house in line water filter. I picked an inexpensive filter unit for about $10.00 plus the wrench for a few dollars more. Some housings are clear, some not, it should not make a difference which you use. Be sure to get one with 3/4" pipe connections that will take the standard 10" filter cartridge.
To connect the system up, you will need tubing and connectors. The connectors must mate with the connectors on the pump and filter housing. If you use any other parts or equipment, make sure all connectors match. The pump I picked needs two plastic garden hose connectors for the pump inlet and outlet. For the filter housing I found two plastic connectors with a 3/4" male thread on one end, the other end has a barbed push on end. The barbed end holds the plastic tubing. The tubing I used is food grade vinyl tubing, 5/8" inch diameter. You may need 10-15 feet depending on your setup.
A pressure gauge between the pump and the filter will help you determine when the filter is plugging. The gauge is not a necessity, but is nice. If you do decide to put one on your system, use one that is rated for 60 psi or less. You will also need a "T" barbed push on connector for a pressure gauge if you use the gauge. Match the "T" ends to all other connections.
A filter system without a filter cartridge is not much more then a fast way to transfer wine. For filtering, you need a 1 micron or finer cartridge. I have in my wine cellar a set of 10" cartridges include 1.0, 0.45, and 0.2 nominal micron sizes. I use the 1 micron size for preliminary filtering, but use the 0.45 or the 0.20 micron for finer filtering. I ordered my cartridges from Presque Isle, 1-800-488-7492 but other suppliers may also carry the filter cartridge. The filter cartridges can filter 50-600 gallons of wine depending on the cartridge and the wine being filtered. See information at the end of the article about a cartridge storage container.
Miscellaneous Parts. You will need 5 hose clamps that will fit over the tubing when installed over the barbed connectors and a little Teflon tape to install the filter connectors.
Hooking it all together. I first started by making a frame on which I could mount the filter and pump. I used a piece of plywood 1' X 2' X 1/2" and built supports to make a stand. I used a couple hooks and straps to hold the filter onto the plywood. I secured the motor/pump to the plywood on the opposite side of the filter. Next, using Teflon tape, install the 3/4" barbed filter connectors into the filter input and output openings.
Measure the distance between the pump output and the filter input. This will be about 1-2 feet long allowing for a bend radius. Cut a piece of the tubing to length, and two more pieces about 2" long. Heat the two short pieces and one end of the 2 foot tubing in boiling water for a few minutes. CAUTION, THIS TUBING IS HOT AND CAN BURN IF HANDLED IMPROPERLY. This will soften the tubing enough to allow you to push it over the barbed ends of the "T" connector for the gauge. Connect the tubing from the "T" to the filter input connector you have already installed. The gauge is connected onto the tubing on the tee end. Install a garden hose clamp to the other end of the long tubing. (SEE DRAWING FOR TUBING CONNECTIONS)
There are two other pieces of tubing needed, the supply tube and the output tubing. Determine the length of tubing needed from your supply carboy into the pump. Cut the tubing to length (or cut the remaining tubing in half), and install a garden hose clamp on one end. Screw that end onto the pump input side. This is your input or supply hose. Take the other tubing and heat one end in boiling water, again being careful of the temperature. Push the tubing onto the barbed end of the filter output connector. This is your output hose and will output filtered wine into a clean carboy.
Secure all connections to the pump, filter housing and gauge using hose clamps where needed. Fill a bucket with 5 gallons water. Add a 1 teaspoon metabisulfite to the water. Put both the input and output hoses into the water. With no filter cartridge installed in the housing, plug in the pump motor power cord. The water will be pumped throughout the system cleaning and sterilizing it. Run this 5-10 minutes, flushing out the system and checking for leaks. Remove power and seal any leaks that you find. Dump the water, and refill with clean water. Run pump again for a few minutes to flush system. Remove power and drain water from tubing and filter housing. (Optional-rather then plugging and unplugging the motor power cord, you could add a switched outlet to the wooden frame. Use the outlet and switch to turn the motor on and off.)
To filter wine, install a cartridge into the filter housing. Put a gallon of water and 1/4 tsp. metabisulfite into the supply carboy. Put the input tubing into the supply carboy and the output tubing into an empty output carboy. Run pump until supply carboy is empty. Rinse the sulfite water in the output carboy. Do this each time BEFORE and AFTER filtering wine-it cleans and sterilizes the system.
Rack the wine to be filtered into your supply carboy, make sure the wine is balanced. Add a double strength metabisulfite to help reduce oxidation, the filtering does have a tendency to bubble at the beginning and end of the carboy. Plug in the cord for the pump motor. The wine will be filtered and pumped into the output carboy. Remove power when the supply carboy is emptied. Bottle your filtered wine.
Since you may not be ready to filter as much wine as the cartridges can filter, you might want to make a container to store the cartridges. Using 3 inch PVC pipe, cut to about 12 inches for each cartridge you want to store. Cement a cap on one end, and make a removable coupling on the other end. The cartridge can be stored in the pipe in a solution of 1200ppm metabisulfite in water. Don Schiller