December 10, 2010


New skimmers are several hundred dollars. I couldn't justify spending that on what is basically a plastic box. So I built my own and saved bigtime. I couldn't find a good step-by-step guide on how to make a homemade pond skimmer. So I have built my own version and explained how I did it. My skimmer has been in use for several months now, it works pretty well. I will explain improvements on this model (Gilt2010) as I go.

Step 1) Buy a normal 32 gallon trashcan. It must be a heavy duty rugged version. Also it must be flexible, not brittle plastic.

IMPROVEMENT 1: Get a square trash can instead of a round one. This makes the inlet and outlet connections fit easier. The large inlet connection had to bend the round can to form a tight seal. It worked, but next time I will use a square can.

Step 2) Buy items needed to build skimmer, all items are at Lowes or Home-Depot:
- Small section of sch 40 4" PVC pipe (not the thin sch 30 drain pipe)
- Small section of sch 40 1 1/2" PVC pipe
- Two 4" toilet closet flanges (in PVC/plumbing section). There are a lot of different versions of these. Get the non-adjustable kind that is simply the flange with a 4" connection as shown. Ensure your 4" PVC pipe fits into the toilet flange.
- 1 4-way PVC connector (1 1/2")
- 3 PVC end caps (1 1/2")
- 1 male and 1 female 1 1/2" electrical conduit connectors. It is important that you go to the electrical section, not the plumbing section. The electrical conduit connectors have straight threading. PVC plumbing connectors have NPT threads (tapered). If you buy a normal bulkhead fitting from a boat or pool store you will spend $20-30, this is about $3.
- 1 rubber toilet gasket. These are in the toilet repair section. They have different sizes. Find one with flexible rubber that will snugly fit over the male threads of the electrical conduit connector.
- 4 stainless steel bolts with matching nuts and large washers. Ensure the bolt fits through the holes in the closet flange. Get washers that fit snugly over the bolt but are as big as you can find, you want to spread the force out so you don't crack the closet flange.
- 1 tube of black outdoor silicon caulking. Ensure you get the sunproof/freezproof outdoor formula.

IMPROVEMENT 2: This skimmer will work for small to medium sized ponds and pumps. I have a huge pond with a 2 speed pump (1/8 hp and 3/4 hp). The 4" inlet is too small to run my pump on high so I can only run low speed. Also, if you have lots of leaves or debris that falls into your pond, the smaller 4" opening can plug easier. Next time I will find a way to make a larger, preferably rectangle opening.

Step 3) Mark the location for the inlet a couple of inches from the top.

Step 4) Cut out the inlet

Try and make it as round and smooth as possible.

Step 5) Mark and cut out the hole for the outlet a few inches off the bottom.

Step 6) Place the rubber gasket on the male electrical conduit connector. Place this on the INSIDE of the tank and the female piece on the outside. Dry fit together and ensure it will fit tightly.

Step 7) Build the outlet strainer out of the PVC pieces as shown. Measure the inside of the tank and ensure this will fit at the bottom. Drill lots of small holes all over the entire strainer. The more holes the better. 3 legs of the strainer are capped (with holes drilled in them) and the 4th leg has the male conduit connector on it.

Step 7) Apply a small bead of silicon on the threads of the electrical conduit bulkhead and around the gasket. Snugly attach the strainer to the tank. Ensure the rubber gasket is between the strainer and the inside of the tank.

Step 8) Measure and cut a small piece of 4" PVC pipe to sit under the strainer and hold it level to the outlet. This ensures that the strainer doesn't move or bend which would break your seal on the tank. I used zip-ties to attach the strainer to the 4" PVC support (drilled a hole in the side of the support for the zip-tie to go through).

Step 9) Dig a hole at the desired location in your pond to support your skimmer. SPEND LOTS OF TIME ensuring you get the right height. The skimmer determines the depth of your pond. The water level will be about 3/4 of the way up the opening. Use levels or lasers or whatever you need to ensure you get the right depth. Too low and you won't be able to fill up your pond as you wanted. Too high and the skimmer won't get enough water as it will spill out somewhere else in your pond.

Step 10) Attach the discharge pipe to your skimmer. I had to dig a trench through my back wall of the pond. Ensure the discharge pipe has a slight downhill grade to it.

Step 11) Now you have to place the rubber lining in your pond. At the skimmer, run the rubber lining up the front of the skimmer and fold over the top and back inside the skimmer. DO NOT cut any holes in the rubber yet.

Step 12) Place one of the closet flanges over where the opening is. Punch out the holes in the liner and drill through the wall of the skimmer for the 4 bolts.

Step 13) Spread plenty of silicon rubber around the opening and between all the layers. Put plenty of silicon around the face of each closet flange.

Step 14) Bolt the two closet flanges together. The layers should be: flange, rubber lining, tank wall, rubber liner, flange. With silicon rubber between every layer. Tighten until the silicon squeezes out, don't overtighten and crack the closet flange.

Seep 15) Allow the silicon to dry completely. Then cut out the two layers of rubber lining inside the flanges and any excess silicon. Make the inside as smooth as possible.

Step 16) Take a 10-12" section of 4" PVC pipe. Cut a 45 degree angle on one end of the pipe on the bottom half of the pipe.

Step 17) Put two screws through the pipe so they are sticking out at about the 10 o'clock and 2 o'clock position opposite from the 45 degree angle cut.

Step 18) Dry fit the pipe into the inside closet flange. This does not need to be glued, it should hold tight on its own.

Step 19) Buy a small nylon mesh tarp from Northern Tool. This is a very fine mesh material and will stop small pieces from getting into your pump. Cut a hole just large enough to slide over the 4" PVC pipe on the inside of your skimmer. Cut the tarp to fit all the way into the skimmer. Use a lighter to melt the cut edges so they don't fray. Fit the tarp inside the skimmer and secure to the outside of the tank (I used large binder clips, but these rust).

Step 20) Use any large mesh nylon bag with a pull string on one side. A small laundry bag works good. Don't use natural fibers, must use nylon or other plastic that won't rot.

Step 21) Attach the mesh bag around the 4" PVC inlet pipe. Pull the cord tight so no leaves can get around the bag. The two screws hold the bag in place. The 45 degree cut on the bottom of the pipe allow the water and leaves to fall freely into the bag without plugging up because the bag hangs down. Without the 45 degree cut on the pipe, the bag will hang over the opening and leaves will plug it.

Your Done! I covered mine with a fake rock from
I have found that I have to dump leaves out of the bag regularly, but haven't had to clean the mesh tarp but about once a month.

Hope this was beneficial!
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  1. I really liked this step by step blog with pictures. It is really informative and I am trying to do all the research that I can to install a koi pond. I have zero knowledge and I think that I can easily do this method that you have explained and I will be sure to make mine with the improvements you posted. I just have a question. All other info I have on skimmers is that they only run a half hour to an hour a day as needed, but I noticed that yours is attached with the pump pulling water from the skimmer barrel and then into a bio filter from there. If the skimmer is constantly running, does it make it harder for your fish to eat? Does it pull the food into the skimmer before they can clean it up?

    1. Yes, I run mine 24 hours a day. Sometimes it sucks up some food, but usually they get it all before. Its a pretty big pond. Good luck on your pond. Best rule I've come accross is make it bigger and deeper than you think you want. After you put all the rocks and stuff in it it is much smaller. I wish I would have made both mine deeper!

  2. Well done!

    I have a slightly different idea in mind (because I have these things available ;->) . Mine involves a submersible pump with float. Build the bucket just as you do, but with a 'return' sized to the submersible pump outflow. (1 1/4" in the case of the submersible I'm using.)

    Cut the trashcan lid to fit toward the bottom of the can, just over the top of the pump, punch it full of 1/2" holes (or smaller if you like, but not necessary) and insure it is 'supported'. I will use 4" sections of gutter drain pipe, as they are rugged and will provide great support - and they are plastic. Buy a 'buffer' (or 2) pad at Home Depot get the size that will fit on the top of the 'holey lid', or trim to fit. Use the 'string bag' as you do.

    This also doubles (somewhat) as a bio-filter because of the buffer pad. Given that you have the buffer pads in there - although I would also use a separate biofilter too.

    The key here is to insure that you don't get debris in the 'sump', or bottom of the trashcan, as these sump pumps use an impeller and it could get clogged, although it isn't all that likely. No matter what you use, you have to filter out the debris else it either clogs the basket/pads/bag/pump or it ends up back in the pond. Not what you want.

    Anyway, thanks for this! It has filled me full of all sorts of project ideas! Off to the workshop!

    1. Good luck! Koi ponds are a fun project! Yes I have a separate bio filter using a large heavy duty plastic storage box and about 100 green scrub pads from an online janitor supply company.

  3. Love the idea of the pond surface skimmer and it does seem to work. I do like the idea of DIY Pond Skimmers and Pond Filters. I used a DIY Pond filter on my pond and it worked a treat and it cost me no where near the price of some filters that are on the market today.

    Holiday Aquatics