4" Counter Current Skimmer

Bill of Materials and Assembly Instructions

Please read the Skimmer Design 101 FAQ so that you can choose the proper size skimmer for your tank.




Click here for a picture of the drain parts.


A 4' to 6' tall reactor body would be a good size.

I will put part numbers by everything I can along where you can get them mail order. You should be able to find most if not all of it locally but my references will backup my descriptions.

Mail order parts suppliers:
US Plastic USP
PlumbingSupply.com PSC
Aquatic Eco-systems AES

Pipe Fitting Legend:
NPT National Pipe Taper
MNPT Male National Pipe Taper
FNPT Female National Pipe Taper
Slip Normal PVC glue fitting
Street Fitting had the same OD as PVC pipe so it will slip inside a slip fitting
Spigot PSC term for a street type fitting

Parts List:
A 10' stick of 3/4" PVC pipe - drain plumbing
B 10' stick of 4" PVC pipe - skimmer body
C 4" Quick Cap - skimmer body bottom USP #30624
D ¾" PVC slip x slip elbow - outside top elbow in drain pipe PSC #406
E ¾" PVC slip x MNPT elbow - internal drain elbow PSC #410
F ¾" PVC slip x slip x FNPT tee - external lower drain tee PSC #402
G ¾" PVC slip tee - anti-siphon for drain PSC #401
H ¾" slip cap - top of anti-siphon tee PSC #447
J 12" of 4 1/2" OD clear acrylic tube - Collection cup AES #TA5
K ½" gray poly Insert x FNPT elbow - external water supply connector AES #119A
L ½" slip x MNPT elbow - internal water supply PSC #410
M 4" x 2" Flexible Coupling - top of 4" PVC pipe USP #30550
N 4" x 2" PVC reducer coupling - bottom of collection cup
O ½" gray poly Insert x MNPT male adapter - collection cup drain. AES #103A
P ¾" compression coupling - used to set water height in skimmer PSC #PCC075
Q ¾" PVC street elbow - skimmer drain PSC #409
R ¾" PVC ball valve - skimmer drain PSC #PVCBSS07
T 6" of 2" clear PVC pipe - Bubble Neck AES #C105

Additional Parts:
6' of rigid airline
3' of flexible airline
2 airline tees
3 wooden airstones
An air pump that can handle the head pressure like a Tetra-Luft pump

Goo Gone is great stuff for removing those pesky labels that are on PVC fittings. You can get Goo Gone and Marine Goop from Home Depot or Lowes. I have found that UniBits work great for drilling acrylic and PVC without any chipping or cracking. Enco has the best price that I have found for them. If you have trouble finding the 7/8" hole saw Amazon's Tool Crib has them. The 7/8" hole saw is a Dewalt DW1825. You will need a mandrel for these and it is a Dewalt DW1800.

You can buy ready made wooden airstones and That Pet Place which has a good price on them. You can also make them yourself out of limewood or basswod airstones 1" x 1" x 4" or 6". I got a 4" x 4" x 24" piece of basswood on Ebay for less than $10 and it made 64 airstones. This is a LOT cheaper than buying them. You could also make one of KW's diffusers as seen on Reef Central. The plans and pictures are in the DIY section of my web site. If you need a gate valve to regulate the input water supply US Plastic has the best price on them by far.

Tools:
7/8" hole saw
1/4" drill bit
saw for cutting PVC
clear PVC cleaner
PVC glue
roll of Teflon tape (pink)
Marine Goop
Goo Gone

 

Assembly:
1 Cut a piece of the 4" PVC pipe 4' to 6' long
2 Drill a 7/8" hole 6" from the top of the 4" PVC pipe.
3 Drill a 1" hole 3" from the bottom of the 4" PVC pipe, on the opposite side of the pipe from the 7/8" hole.
4 Apply Teflon tape to the threads of the 3/4" PVC slip x MNPT elbow.
5 Install the 3/4" PVC slip x MNPT elbow from the inside of the 4" PVC pipe with the MNPT through the 1" hole at the bottom of the 4" PVC pipe.
6 Screw the 3/4" PVC slip x slip x FNPT tee onto the 3/4" PVC slip x MNPT elbow. The 3/4" PVC slip x MNPT elbow should be pointing towards the top of the 4" PVC pipe. The 3/4" PVC slip x slip x FNPT tee should be pointing toward the top and bottom of the 4" PVC pipe.
7 Apply Teflon tape to the threads of the 1/2" slip x MNPT elbow.
8 Install the 1/2" slip x MNPT elbow from the inside of the 4" PVC pipe with the MNPT through the 7/8" hole.
9 Screw the 1/2" gray poly Insert x FNPT elbow onto the 1/2" slip x MNPT elbow. The 1/2" gray poly Insert x FNPT elbow should point towards the bottom of the 4" PVC pipe. The 1/2" slip x MNPT elbow should end up 90 degrees to the 1/2" gray poly Insert x FNPT elbow so that the water comes out and goes around the inside wall of the 4" PVC pipe.
10 Use Marine Goop to seal the 3/4" PVC slip x slip x FNPT tee onto the 3/4" PVC slip x MNPT elbow in their hole in the 4" PVC pipe. Use Marine Goop to seal the 1/2" gray poly Insert x FNPT elbow onto the 1/2" elbow slip x MNPT in their hole in the 4" PVC pipe. If you have not used Marine Goop before, it is thick, but once you put it on it has a tendency to run, so keep this in mind. Because these fittings are on opposite sides of the 4" PVC pipe you will only be able to glue one of them at a time.
11 Glue the 3/4" PVC street elbow in the bottom port of the 3/4" PVC slip x slip x FNPT tee. Glue a 1 ½" piece of 3/4" PVC pipe between the 3/4" PVC street elbow and the 3/4" PVC ball valve. You could put a garden hose connector (GHT) fitting on the ball valve so you could use a garden hose to drain the skimmer. PSC has male and female GHT to slip or spigot fittings.
12 Glue a piece of 3/4" PVC pipe in the top port of the 3/4" PVC slip x slip x FNPT tee.
13 Glue a piece of 3/4" PVC pipe in one end of the 3/4" PVC slip x slip elbow.
14 Install the 3/4" compression coupling between these two pieces of ¾" PVC pipe, with the pipes each 2" into the 3/4" compression coupling. The top of the 3/4" PVC slip x slip elbow should be 2" from the top of the 4" PVC pipe. The reason that I did not specify the length of these two pieces of ¾" PVC pipe is because I do not know how tall you skimmer body is. The 3/4" compression coupling will help you adjust the water level in the skimmer. If you need to lower it more than the 3/4" compression coupling will allow, just cut a short piece off of either one of the pieces of ¾" PVC pipe.
15 Install the 4" Quick Cap on the bottom of the 4" PVC pipe and tighten the clamp.
16 Once you know where the skimmer is going to sit in relation to the tank or sump. Cut a piece of ¾" PVC pipe that runs from the ¾" PVC slip x slip elbow to just over the inside edge of the tank or sump. Glue this piece of 3/4" PVC pipe into the open end of the ¾" PVC slip x slip elbow. Glue the side port of the 3/4" PVC slip tee onto the other end of the ¾" PVC pipe with the end ports of 3/4" PVC slip tee pointing straight up and down. Glue a 3" long piece of 3/4" PVC pipe in the top port of the 3/4" PVC slip tee. Drill a ¼" hole in the top of the 3/4" slip cap and put it on top of the 3" piece of ¾" PVC pipe. Glue a piece of 3/4" PVC pipe in the bottom port of 3/4" PVC slip tee that extends down into the tank or sump water 2" - 4".
17 Drill a ¼" hole in the sloped part of the 4" x 2" Flexible Coupling for the flexible airline to pass through. If you use more than one air pump, drill a hole for each pump. Push a piece of airline through each hole with 4" - 6" on the inside and about a foot on the outside. You will put an air control valve(s) on the line(s) so that you can have fine-tuning of the air pump(s) output. Assemble the rigid airline, tees and airstones. Lower them into the 4" PVC pipe. Trim the rigid airline when the airstones are two inches above the floor of the skimmer and attach them to the flexible airline(s). Sit the 4" x 2" Flexible Coupling on top of the 4" PVC pipe and tighten the clamp. At this point the skimmer base is done.
18 Now it is time for the collection cup assembly.
You will need to remove the ridge from the inside of the 4" x 2" PVC reducer coupling so that the 2" clear PVC pipe can pass clear through it. This is the worst task in the whole job. Drill a 7/8" hole for the 1/2" gray poly Insert x MNPT male adapter and glue it in. Glue the 2" clear PVC pipe into the 4" x 2" PVC reducer coupling with a bead of Marine Goop around the outside edge of the 2" side of the 4" x 2" PVC reducer coupling. You may need to notch the 4 1/2" OD clear acrylic tube so that it does not interfere with the drain hole. Do not glue 4 1/2" OD clear acrylic tube to the 4" x 2" PVC reducer coupling so that you can remove it for easier cleaning. You can use a 4" x 2" Flexible Coupling in place of the 4" x 2" PVC reducer coupling so that you can take the unit apart at will. It won't look as nice but it will be easier to assemble and service.

It is now time to turn the water on and check for leaks. Next turn the air on and adjust the water and air level. After the skimmer has run a few days and has "slimed up" inside it will begin to really operate and so the water and air may need to be adjusted again.