This web page has pictures and instructions on building my version of the Rubber Maid stock tank filter. The picture at the top of the page is of a pond built by a young woman in NC this year (2003) using a Rubber Maid stock tank with these instructions.

Gene Winstead
Koi Village

NOTE: The stainless steel spillway is designed to fit the 100, 150 and 300 gallon stock tanks. The 100 gallon tank measures 52"L x 30"W x 26" deep. The length and width are the same on the 150 and 300 gallon tanks but they are wider. The 300 gallon tank is almost as wide as it is long.

The pictures below show the 100 gallon tank. If you use a 150 or 300 gallon tank you'll need more material for the spacer and more filter media. All the other parts are the same. Once you have all the materials and tools needed you can build one of these filters in an hour.

Our commercial site:  http://www.koivillage.com

Improved design October 18, 2004

Parts Needed

Two - 2 inch shower drains
Two - 2 inch bulkhead fittings
Two - 2 inch 90 degree elbows
One - 2 inch Tee
One - 3 inch Tee
Two - 3 inch x 2 inch adapters One - 3 inch knife valve
Two - 2 inch male x socket adapters
Two - 2 inch male x female street elbows
5 ft - 3" PVC pipe
5 ft - 2" PVC pipe (5 feet is the smallest size you can buy PVC pipe.)
One - stainless steel spillway
Nine - 1/4" x 1" stainless steel bolts with self locking nuts
One 2' x 4' poly spacer (You can use the 2' x 4' plastic egg crating used for a floresent light cover available at Lowe's, Home Depot or other home improvement center for the spacer but it isn't as sturdy. If you use the 150 gallon tank you'll need two of the spacers and the 300 gallon tank requires three.)

Tools Needed

Drill (If you use a hole saw it will take one 3-1/4" in diameter.)
15/64" drill bit
Jig Saw
Side grinder or sharp wood chisel
Screw Driver (phillips or flat blade, depending on the screws)
Sand paper

I used a side grinder to remove the excess material so the shower drains will fit. You can also use a sharp wood chisel. You only have to remove enough so the nut of the shower drain will fit. Be sure to get the area level so you will get a good seal.

Use the sand paper to clean-up around the inside and outside of the holes. I used "Plumbers Goop" where the drain comes through the bottom of the stock tank to insure a good seal. Silicone can also be used but having used both I prefer the "Plumbers Goop".

Center the spillway at the top of the tank as shown. Be sure it is on the same side as the factory bottom drain. The ribs inside of the tank doesn't allow the spillway to be installed on the other side. The white plastic film on the spillway is to protect it from scratches during shipping and handling. We have these spillways made by a manufacturer of restaurant equipment. It is a high grade of stainless. You can peal the plastic film off once the filter is built.

I use a "Sharpie" fine point felt tip pen to mark the tank on the inside of the spillway. Be sure you have the spillway pushed up as far as it will go before making your marks. In order to insure the screw holes fit well I use the drill to mark the holes for the bolts. At this time I also drill a couple holes on the inside of the area to be cut so I can start my jig saw.

Once you have made the cuts across the bottom and as far up each side from the outside of the tank you'll need to finish the vertical cuts and the top horizental cut from the inside of the tank. Mounting the spillway is the last thing you do since the liner from the pond or stream bed should be sandwiched between the spillway and tank. This not only acts as a gasket but also prevents water from getting behind the liner. The two most common areas where people encounter leaks are their waterfalls and faceplates on skimmers.

My first design on this filter only had one 2" bottom drain and it was placed on the side close to the bottom with a 2" elbow turned down on the inside. While that way made it easier to set the tank it just didn't work as well as I'd like. When using bulkhead fittings they stuck up too far on the inside of the tank to allow good drainage but with the shower drains they mount almost flush with the bottom of the tank. I'm using the 3 inch main drain since it will handle the volume of two 2" drains. Each increased size in pipe will double the volume of water that will flow through that pipe. The faster you can drain the tank the better removal of debris. You can get by with using a 2" Tee and 2" knife valve.

In order to insure the inlet holes are positioned properly use the outer nut from the 2" bulkhead fitting and position it on the tank so you will be sure you can tighten it when installed. Draw around the inside of the nut and then find the center of that ring so you'll know where to start the hole saw drill bit.

NOTE: If you are in a climate that experiences freezing in the winter be sure to insulate your pipes and use heat tape if necessary! If you normally shut down your filtration in the winter be sure you completely drain the filter and pipes. Use a shop vac on reverse to blow out any water in the lines and cover the tank so rain can't fill them again.

The 3" drain pipe should be cut long enough so when the knife valve is mounted it will allow you to operate the handle between the tank and the inlet pipe.

When you have the filter positioned at the pond or the head of the stream run the liner up between the filter and spillway to form a gasket. The picture below shows a small piece of EPDM I used for demonstration purposes. Use some silicon or Plumbers Goop between the liner and filter tank as well as between the spillway and liner. Once you have the bolts installed and tightened use a razor knife to cut the liner along the bottom and sides of the spillway. I use a large nail to make the holes for the bolts.

The 2" male x female street 90 degree elbows should be installed on the inside of the inlet bulkhead fittings so they point in opposite directions and are turned just slightly downward. This will help wash the bottom when back flushing the filter. I am well pleased with the flow pattern I'm getting from this new design.

Once you have the tank positioned, the inlet connected and have checked for leaks you can put in the grating and filter media. There are many different types of media that will work for this filter. That is your choice. One media that is working very well with this filter is the Savio Springflo. It takes three rolls for the 100 gallon tank. On the first design I recommended a piece of filter pad be placed on top of the grating before the main biological media. We have found that the Springflo works very well without the pad.

I set the first one I built up on a 1000 gallon reservoir tank to test it. The pictures below show a flow rate of 3,000 gallons per hour. This is a good flow for the 100 gallon tank. The spillway can handle twice that flow if you use it on a larger tank.

Below is a way to configure the inlet so you will have a very accessible water source from the pond to rinse the filter and media. You should always use pond water to rinse the filters and media so you don't shock or kill any of the beneficial bacteria with chlorine from tap water or a drastic change in water temp. You should back flush the filter at least once per week during the warm season when you are feeding the fish and remove 10% of the pond water.

Open the 3" knife valve and drain the water to a garden or waste. Leave the pump running. Once the tank has drained and the water is rinsing the bottom of the tank connect a short garden hose to the spigot. Open the spigot and slowly close the ball valve on the inlet pipe until you have a good stream of water coming from the hose and rinse the filter media from the top down. Once you have drained 10% of the pond water shut the 3" knife valve and add fresh water to replace what you drained out. Always use a dechlorinator when adding new water. If the filtration is shut down during the winter you can disconnect this type of ball valve after you drain the tank.

I hope this web page helps you with your filter needs. If you have any questions about my design just email me and I'll try to answer them.

© Copyright 2002 - 2005 Koi Village. All Rights Reserved.