The Expanded Air Process (EAP) Skimmer FAQ.

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This document may not otherwise be published, posted, uploaded, replicated or copied by any method, electronic or physical, without explicit permission.

The author is not liable in any form or fashion, nor are his employers, for how you use this information.

Revision history:

It is my intention to do a photo shoot of the various assemblies. get them scanned, and work them into the document. So expect Revision 2, it will be much more useful.

Questions and comments about this FAQ may be directed to "wkirk@snip.net". Please limit these to the design, construction, and operation of the EAP, or the improvement of this FAQ.

Contents:

What is an "Expanded Air Process" Skimmer?

This type of skimmer was first marketed by Marine Technical Concepts, Inc. through a product line they call the HSA (High Speed Aireation) series. The key feature of these skimmers is their use of a commonly available fountain head used for lawn and garden ponds. The fountain head is manufactured by Beckett, who calls it a "Foam jet fountain head".

The Expanded Air Process skimmer is a skimmer built around the Beckett head.

Where do I get such a skimmer?

MTC sells a professional acrylic device which is held in high regard by a number of newsgroup posters. MTC shows a good set of pictures, one with the unit in operation, on their web page http://www.marinetechnical.com.

It is rumored that other manufacturers are working on models of their own.

Or, you can build one.

How big of a pump do I need?

The original version of the skimmer used a Quiet One, which is rated at 1100 GPH at zero head. Some have reported using pumps with higher ratings. One pump reported to be working was rated 1500 GPH at 6'. Devices using lower rated pumps haven't been reported.

Where do I get this Beckett Foam Jet?

Chris Paris of CMU posted this image of the Beckett head. It can be found where lawn and garden ponds are sold. There are mail order sources that can be found on the net. Retail price at Home Depot was $15.

How does the Beckett work?

It is a venturi valve. Water is pumped in (image left), it sucks air in from the side (image center), and an air/water mix is ejected (image right). Below is another image from Chris's site that shows the inner details of the Beckett.

Unlike valves found on traditional venturi skimmers, the Beckett pulls a great deal of air into the air/water mix.

Is a DIY version of an HSA type skimmer possible?

Many have claimed that "it can't be done". However, if one took all the various pieces used to build a commercial version and put them together properly, one must assume it would work. So, at least we know it can be done.

The skimmer described below should be easy enough to build for anyone with basic PVC pipe fitting skills. With a little care, even a novice should be able to succeed.

Are we building a clone of MTC's HSA products?

No. This skimmer does not look like MTC's HSA. It better resembles the ETS "downdraft" style of skimmer, but the resemblance is only "skin deep". The internal designs of this and the ETS are quite different.

I've heard about a DIY "Super-HSA", what is that?

This is the same skimmer. The term "Super-HSA" was used over the course of the newsgroup discussion to highlight the "Super" low cost, and contact time of this skimmer over other HSA type skimmers.

Even thought MTC's web site doesn't indicate they have registered "HSA" as a trade mark, I feel this version of the skimmer can stand on its own as the "EAP".

So, What is this skimmer officially called?

The "EAP-2".

"EAP-1" is reserved for the possibility of a smaller version.

I've seen a 4" foaming head spouting a jet about 6' high at a local shopping mall. Perhaps we should reserve "EAP-3" for the first to build a workable skimmer around that puppy, any takers?

Where do I get the other parts?

The PVC parts were bought at Home Depot, but most any builder's store should have the fittings, tube, and Beckett head. A fair sized pump is needed, and there may be better sources than Home Depot for these. The original version used mail ordered 2" and 4" clear PVC tubing.

How big is the EAP-2?

It stands 4', floor to calling. It has a footprint of 5"x17". The height can be easily reduced to 3'.

To get under 3' will probably require more extensive design changes.

How big a tank does it support?

It supports tanks up to the size of the pump's ability to turn over 1 tank/hour. Pump size is limited by the skimmer's ability to handle the flow.

If the flow is 900GPH, then it will support a 900G tank, etc. I base this estimate only on information found in the "Reefkeepers FAQ". This skimmer might do better than this, and I doubt it can do any worse.

Flows rates between 900 GPH and 1500 GPH have been reported to work. The original version handles about 900 GPH (Quiet One @ 4' head).

Will the EAP pull more gunk from my tank than my current skimmer?

Who knows. In the author's opinion, probably. Every tank is different, the same tank varies over time, each tank produces different sets of proteins, and every installation is different. I suspect there are just too many variables for a controlled experiment to produce meaningful results that cover every application. Sorry about that.

A tank only produces so much gunk per day. A 100% efficient skimmer will pull it all out on the first pass through. Nothing is 100%.

If a good skimmer is compared to a lesser one, both might still pull about the same amount of gunk per day over the long term. They are merely matching the tank's output. Here are some of the differences between a better and lesser skimmer...

The better skimmer produces more gunk in the first few days, then settles back to the same rate of production. If so, then the better skimmer is probably keeping the organic count lower than the lesser one. The spike was the better skimmer lowering the count. The tank should produce fewer nitrates over time.

The better skimmer produces less, but more concentrated gunk. This may be hard to detect by eye, since many proteins are clear (like egg whites). Some believe skimmers that produce more concentrated gunk pull fewer trace elements from the water, but again, who knows.

The better skimmer may shine in peak situations, like death of a specimen. It may be able to purge the water more quickly.

The EAP was built to get the most out of pumps in the same class as the Quiet One. Many people are running "big pump" skimmers, such as venturi, downdraft, and HSA. If you have a big pump, why not get the most out of it? This was the design goal for the EAP. It should prove a worthy skimmer.

Has anybody else built an EAP, what did they think?

Shawn Ramsey appears to be the first to pick the EAP off the Newsgroup and build one. The first response started with "Wow.", and went on to say "I am very happy." Later postings continued to suggest the device was working well.

Shawn reports to be using a 1500 GPH pump.

Shawn's observations about operation of the EAP appear to confirm those made of the original version.

NOTE: To insure verification work had actually been done, some information was not posted to the Newsgroup. One such detail was the quality of the foam output. The original version often ejects a thick foam that can take hours to break down. Shawn has reported the EAP was ejecting foam "like shaving cream".

Do I have to use clear PVC, its so expensive?

It is highly recommended. It helps show what is going on inside. It helps suggest when it needs cleaning. It's fun to show your friends... Well, maybe not.

Don't be too cheap, this is a state-of-the-art device. Do it right the first time, and it won't have to do it again. The clear PVC will add to the cost, but that is nothing compared to a commercial version.

The pump will run $100, so why not budget the same for the skimmer itself?

Can I use Acrylic?

There is such a thing as extruded acrylic tubing that is size compatible with Schedule 40 PVC fittings. It runs about 50% of the cost of PVC. It is more clear, but it is only 1/8" thick.

It has been reported that extruded acrylic is more likely to crack when glued than the cell cast form. However, cell cast is more expensive than extruded.

It would seem that acrylic can be cheaper and allow for greater visibility, at a cost of strength and higher potential for algae growth inside. PVC is more costly, stronger, and adds a small degree of cloudiness to the tube walls.

Feel free to substitute acrylic for PVC throughout the design. In the worst case, shorten the downtube slightly to make up for the larger inside diameter of the 1/8" tube walls. 30" should be fine.

Where do I get the plans?

Right here. This is the most FAQ of them all.

The rest of this document is dedicated to building an EAP-2 skimmer.

Some of this is different from what I read in the Newsgroup, why?

Every aspect of the design was reconsidered as the FAQ was prepared. If something wasn't needed, or could be done in an easier way, an update was made to the plan. These updates were first applied to the author's EAP.

The most updated version of the plans are reflected in this FAQ.

What are the major components of the EAP-2?

The skimmer has the following major pieces.

The Beckett containment chamber.

The downtube.

The sump.

The riser.

The drain.

The gunk collection system.

There are two optional accessories, for that professional touch.

The "overflow proof" collection bottle.

The carbon air filter.

You just gotta have a picture, don't you?

Yes. This was known as the "horrid little gif" in the newsgroup thread. It is enough to give the general idea of the detail that is to follow.

One day soon, I'll do a photo shoot of the various assemblies and incorporate the scans into the FAQ.

What is the "Beckett containment chamber"?

The Beckett is probably the first skimmer technology that draws too much air into the air/water mix. Skimmers based on it seem to need some way of de-optimizing this much flow. One way is to restrict air flow into the Beckett head.

It turns out that restricting the air flow makes the Beckett's bubbles smaller. As most who know how skimmers work are aware, smaller bubbles are better bubbles. At least smaller is better until they start floating into the tank.

So, the Beckett containment chamber controls the flow of air into the skimmer. It also happens that the Beckett spits water, something we have to stop. Then there is the fact that a great deal of air will be blown through the tank water, and it would be a good thing if we could filter that air.

A containment chamber lets us take care of these various problems by turning the Beckett into what amounts to a pipe fitting.

How do I build the "Beckett containment chamber"?

The containment is a 1-1/4x1-1/4x1/2" "T", and two 1-1/4"x1" bushings. The Beckett is simply glued and compressed between the two bushings inside the "T".

To do this...

You will need the above fittings and a tin of "All purpose PVC, CPVC, ABS" glue. Cut two fitting-to-fitting lengths of 1" tube.

Rip the Beckett out of its package. Pull the slip ring off the output side of the head (The ring is to the right side of Chris's Beckett images). Discard the ring.

The Beckett will not fit through through the 1" part of the bushings, but will slide through the 1-1/4 part of the "T". Fit one of the bushings into the "T", then the Beckett, then the other bushing. Note the orientation and disassemble. This is how it glues together.

Notice the input side bushing sits on the first fin of the Beckett's frame. Slop a good bit of all purpose glue around this ring, and apply the bushing to the Beckett. Press, hold hard, and wait 30 seconds for the glue to set. Keep the Beckett true to center.

With the Beckett side down, carefully pour some all purpose glue into the space between the Beckett's input and the bushing. Don't fill the space, just enough to coat the bottom. Then coat the remaining inside of the bushing and insert 1 of the fitting-to-fitting length tubes. Don't push so hard as to break the Beckett off the bushing, it is sealed, it is not strong.

Don't get glue into the Beckett.

Glue the Beckett/bushing unit into the "T". Push in the full depth of the fitting. This will set the Beckett's air input holes at the right level within the "T".

Notice that the other bushing won't fit all the way into the "T". The fitting can be cut, about in half, for appearance. At least 1/2 of the fitting should be able to find a resting place within the "T". Choose to cut, or not.

Glue the other fitting-to-fitting tube into the fitting. If the fitting was cut, there will be no stop. Slide the pipe in only so far as the end of the fitting.

Glue the tube/bushing into the "T". The output of the Beckett must be clamped together within the 1" tube. Push the fitting in firmly, the vise force on the Beckett will keep the unit sound.

YOU'RE DONE. This is the basic containment. The Beckett now amounts to a PVC "fitting" with a 1" water input, 1" output, and a 1/2 inch air input.

How do I add air control to containment chamber?

Apply a 1/2" 90, and 1/2" plastic ball valve to the 1/2" side of the "T". This is the air flow control.

Make sure the ball valve points upwards, so the Beckett's spit will not drain down through the 1/2". The Beckett will recycle any water that leaks/spits within the "T".

Lightly stuff a bit of cotton in the top of the ball valve, to filter dust and other pollutants from the air.

Or, build the optional carbon air filter accessory.

How do I plumb my pump into containment chamber?

Add a pair of 1" 90's to reverse the water flow downwards towards the pump. Perhaps a threaded adapter on the input end of the 180, and a hose barb would be nice if the plumbing is poly tube.

What is the downtube?

The downtube maximizes air/water contact time, and helps insure small bubble size.

Air/water mix flows from the Beckett chamber into the top of the downtube. The air tries to float upwards, but is always being pushed down by the flow of water.

First, this is the way "counter current" skimmers gain maximum contact time between the air and the water. Bubbles collect organics only while they are in contact with the water flow. The counter current downtube keeps the bubbles in the water as long as possible.

Second, the Beckett injects bubbles of various sizes. Some are too large for our purposes. It happens that large bubbles rise faster than small ones, so these big bubbles overtake the water flow and rise to the top of the downtube. Here, the Beckett output jet re-integrates them into the water flow as smaller bubbles. The smaller bubbles get a second chance to be pumped out the bottom of the downtube.

It is unlikely that putting anything, like bio-balls, in the downtube will improve the process. But, its always fun to experiment.

How do I build the downtube?

The downtube is a 33"x2" tube with a 2"x1" bushing on both ends. A 2" union is needed to apply each bushing.

The downtube can be liberally adjusted for size. 33"x2" is probably the maximum geometry, but tubes as small as 20"x1" are known to work. To bring the total height of the skimmer down to 3', use a 21"x2" downtube.

Smaller tubes reduce the efficiency of the skimmer, so tank water has to make more passes though to be cleaned as well as it would have making one pass through the larger tube. Larger downtubes are probably more meaningful on larger tanks.

Feel free to experiment. Just remember the Beckett containment requires a 1" female fitting.

What is the sump?

The sump is the area where the air is separated from the water. The water flows back to the tank, the air flows up into the riser. The downtube, riser, and drain meet at the sump.

How do I build the sump?

The sump is basically an upside down 4" "T".

The downtube and drain connect at sides of the "T"s straight through section. The 4" riser tube connects to the stem of this upside down "T".

Two 4" reducing bushings are needed. One for the downtube side, the other for the drain side.

First, the drain side. This is the easiest to do. Apply one 4"x1-1/2" reducing bushing to the side of the "T". The original version happened to use the sweeping side of the 4" "T" as the drain. (Ask a plumber, the "sweeping side" of the drain is the "politically correct" way for water to drain through a 4" PVC "T" fitting.) If the 4"x1-1/2" bushing is unavailable, then use the more common 4"x2" bushing and apply a 2"x1-1/2" bushing to the 2" hole. All done.

Next, the downtube side. This is bit more fun. The idea is to get a 1" pipe to pass cleanly through this wall in the sump. Since pipes aren't supposed to travel within other pipes, doing this will require a non-standard fitting arrangement. Using the "All purpose" glue is recommended. Don't worry, a perfect and strong seal is easy to achieve.

Glue two 1-1/4"x1" reducing bushings into both sides of a 1-1/4" union. Yes, this is now nothing more than a fat 1" union.

Ok, Notice how the 1-1/4" union will just fit through the 2" hole in the bushing. It is a loose fit, but that is ok. Notice that the 1-1/4" union is also a loose fit inside of a 2" tube. Again, that is ok. The "All Purpose" glue will fill the gaps.

Cut a length of 2" pipe to be flush with the outside of the bushing (about 1"). Glue it into the bushing. Now, apply an excess of glue to the outside of the 1-1/4" union and the inside of the 2" pipe just placed in the bushing. Slip the 1-1/4" union through the 2" pipe (from the inside of the bushing, pushing out) until the union is also flush with the outside of the bushing. Slowly twist the union as it passes through. A puddle of glue should form in the inside disk of the bushing, where the 1-1/4" penetrates. If it does not then pour a thin layer there. Wipe off any gross excess of glue. Let this sit for a few hours. This assembly is a 4"x1" "through the wall" fitting.

DO NOT continue until this part is well set, moving the fitting too soon will cause it to leak!

To finish the sump, apply the 4"x1" "through the wall" fitting across from the drain on the 4" "T". See, not so hard.

Is there special plumbing inside the sump?

Yes. A short length of 1" tube, a 90 degree elbow, and a 2"x1" reducing bushing.

The idea is to center the 2"x1" bushing, facing upward, in the riser. Cut the 1" tube as long as needed to do this. The 1" tube plugs into the inside of the custom made 4"x1" through-the-wall bushing. The 2"x1" bushing sits immediately on top of the 90, connected by a fitting-to-fitting length of 1" tube.

This piece sits inside the sump, it will be covered with water inside and out.

How do I connect the downtube to the sump?

With a 1" 90 degree elbow, and two fitting-to-fitting lengths of 1" tube.

It is important to keep the horizontal run of pipe as short as possible. Keep the 90 as close to the sump as it will fit. Do not extend it away from the sump.

How do I build the riser?

Start with 30" of 4" tube. Apply it to the stem of the sump "T".

Top the riser with a 4" union and 4"x2" reducing bushing. DO NOT glue these parts yet, the riser will need cut down later.

The collection cup will fit into the 2" side of the bushing.

The riser must be tuned to fit. The final height can be controlled by limiting the amount of air allowed to enter the Beckett containment chamber. Less air, lower riser. Details of the drain can also affects riser height. The device must be allowed to work for a few days before settling on a final riser height.

How do I set the Air flow?

This is an art. The Beckett chamber's air valve must be set such that the surface area of the air in the skimmer is maximized. This DOES NOT mean the maximum quantity of air. A reasonable set point should be found between the following extremes.

First, fully open the value. Start closing the valve until there is a change in bubble size. The bubbles will start to grow smaller. This is the highest reasonable set point.

Continue to close the valve, until the water in the downtube appears to grow just the slightest bit less white. Watch closely, just the slightest bit. The bubble size may, or may not, change. You may, or may not, hear a slight change in the tone of the Beckett. This is just under the lowest reasonable set point.

The right answer is somewhere in between.

How do I cut the riser to proper height?

The height of foam riser depends on the size of the pump, how much air is added to the mix, and how the drain is put together. To say the riser should be xx" tall might work for some, but not others.

The riser on the original version happens to be 24" tall and might stand to be 1-2" shorter. This shows that it can be done, and it isn't all too hard.

Cutting the riser is the last step in the construction. This will take a few days, be patient. It is easier to cut more off, than to put it back.

See the section on setting the air flow. Set it to the higher set point. Wait at least 24 hours and note how well the skimmer is doing. It should have a head of dry foam sitting above a column of wet foam. If not, then here are some possibilities...

The air flow is too high, or the pump is too big. If this is the case, the column should continue to grow wet foam all the way to the top of the riser. You must reduce air or water flow to continue.

The tank is not generating enough debris to break in the skimmer as expected. This will show as little or no wet foam head. This can also happen if you are doing something that keeps breaking the tanks skimmer function. Keep hands and feet out of the tank!

There could be a substantial wet foam column that periodically collapses into a better looking and separated wet/dry foam sections. The dry foam is then mixed back into the wet, only to repeat the process every few minutes. This suggests the air flow is higher than it should be or, more likely, the skimmer is not plumb. Check that the riser is truly vertical, if so, then cut the air slightly.

(Note the term "substantial", minor wet/dry foam agitation is nothing to worry about. The key is that dry foam must accumulate in such a way that it will be ejected periodically.)

A good feel for the skimmer should be had in about a week. Pick a point along the riser where the wet foam has never touched, but not so high that the dry foam takes days to get there. Cut the riser here.

The dry foam keeps "rolling into" the wet foam, what's wrong?

Make sure the skimmer is level. The bubbles must rise straight to the top of the riser. If the riser is tilted, air will rise up the high side, and water will run down the low. This will set up a rolling motion that will likely interfere with the formation of dry foam.

How do I build the drain?

See picture, right of the riser. Note that the dashed lines indicate water levels.

Most will need five 1-1/2" 90 degree elbows, and lengths of 1-1/2" tube to fit the placement of the skimmer and the tank's sump. Tube lengths will be unique to each specific installation.

The first 90 comes upward off the skimmer's sump. The next two make a 180 down into the tank's sump. The final two form a "U" trap in the tank's sump to control the level of water in the skimmer.

The "U" trap insures that a siphon will form in the drain tube. This siphon should be set to keep the natural (power off) water level in the riser just above the the 4" "T". Make sure the top of the "U" trap output is at the same level as this part of the "T". The original version had a natural riser water level of 1".

Using this siphon drain design will maintain a steady water level in the skimmer without having to fiddle with flow control valves.

The sump should not be designed such that routine water levels are above the drain's "U" tube output.

How do I build the gunk collection system?

Gunk is collected off the top of the riser with a 2"x1/2" reducing bushing, plugged into 2" union on top of a 5"x2" stem. A pair of 90 degree elbows makes a 180 off the top of the stem pointing downward towards the collection bottle.

Leave a short length of 1/2" tube on the downward pointing 90. This 1/2" tube allows a 3/4" poly tube can be clamped on.

Not much of a "collection cup", but it suits our need.

Why doesn't the EAP have a collection cup?

The traditional collection cup is basically a siphon break. It is needed because gunk siphons would cause water levels in the skimmer to fluctuate. In the worst case, they could draw water over the top, and start draining the system all over the floor. All this because gunk water could fall down through the exhaust tube faster than the air could push it out.

The EAP pushes so much air through the system that siphons aren't likely to form. The air flow will eject gunk from the tube much faster than gravity could pull it down.

I went on vacation and my gunk bottle overflowed! What can I do?

Build an "overflow proof" collection bottle. When such a bottle is full, it will not allow air to escape from the skimmer. This will blow down the riser column and shut it off.

The basic bottle is a 2"x10" tube, with a ping-pong ball inside. The lower end of the tube is sealed with a 2" cap. The upper side of the tube is fitted with a 2"x1-1/4" bushing. The ping-pong ball will not fit through a 1-1/4" tube.

You can friction fit a 3" length of 1-1/4" tube into the top. Force it in with a bit of fiberglass window screen, then you can add a small bit of carbon to the tube and a patch of cotton to hold it in. This will reduce gunk odor.

Now you have to figure a way to get gunk into the bottle, and there are two ways. The artistic yet tricky, and the easy but bulky.

The artistic thing to do is drill a hole through the side and glue a 1/2" 90 degree elbow through the hole, pointing upward. The hole must be just large enough, and cleanly cut, the glue will not seal any large crack. Be sure the ball works freely past the 90, else make sure the ball is caught above the restriction.

The easy thing to do is splice in a 2" "T", and use a 2"x1/2" bushing to reduce the stem of the "T". A 1/2" 90 degree elbow pointing up off the stem of the "T" and its done.

A short length of 3/4" poly tube can be run from the riser's 180 downturn to the collection bottle hookup.

The collection bottle can be clamped to the riser with a "C" support.

How do I get this thing to stand up?

Four "J" hook pipe hangers glued to the sump "T" will help. There is more than one workable configuration. Two of them are...

Clip the hooks over top of the sump "T" in an "A" frame configuration. Cut the legs and adjust the angle to suit. This configuration may be a little easier to level.

Clip the hooks under the "T" like a "J" rolled on its side.

Once settled on the configuration, glue the rounded part of the "J" to the sump.

Shouldn't the downtube be supported?

Yes, it really must be. The 1" elbow isn't all that strong that it can take the force of a 33" pry bar (the downtube) bending on it. Without support, the elbow is sure to break sooner, or later.

Use a "C" support to clamp the downtube to the riser.

What is a "C" support?

Build a "C" support out of a 4" and a 2" PVC J-hook hanger. Cut enough off the long end of the "J" hooks to keep the 2" downtube aligned with the riser. Glue the "J" hooks one on top of the other in an elongated "C", and clamp. The two hooks will overlap about 3.5".

These "C" supports are also be used to attach the gunk collection bottle and air filter to the riser.

How do I build an air filter?

The air filter is much like the collection bottle, only the 1/2" uptube is fixed to the bottom rather than the top. The 2" portion can also be made smaller.

The original skimmer uses a 2"x10" tube and a 2" cap. It has a 3" bed of fiber floss in the bottom, about 5" of carbon, and some floss on top to hold it together. A 3/4" poly tube connects the filter to the air control valve on the containment chamber.

The top floss gets quite dusty, it should be replaced more often than the carbon needs to be.

"Fiber floss" on the original version is the fiber material from an old 3M "Filltrete" air filter. This material is a superior particle e filter, if you happen to have it around.

The filter is clamped to the riser with a "C" support.

Ok, really, what should NOT be glued together?

The containment chamber has a 1" male output tube. This should friction fit into the female fitting at the top of the downtube. Pressure here is near zero, so leakage should not be a problem.

The 4" union should be glued to the top of the riser, but the 4"x2" bushing should not be. The bushing must be removed to clean the riser.