A cheap PVC skimmer

[Mr. Fosi]

I am building an all PVC skimmer.

 

I have some uncured LR coming in three days and I want to have something to skim with when it gets here.

 

I have been all over the place looking at different designs and they are all pretty similar (other than UTR's magic box)

 

I am using all PVC b/c it is the cheapest option for me (yes I know I won't be able to see the bubbles).

 

Here is a diagram of what I am proposing:

 

 

Here are pictures of what I have done so far:

 

Skimmer body and top cap

 

 

Collection cup and neck (yet to be cut to size)

 

 

Another view of the collection cup and neck

 

Questions to be answered:

 

(1) Do I need back pressure to eliminate micro bubbles?

(2) Will 3/4" inlet to 1/2" outlet create enough back pressure to eliminate microbubbles?

(3) Should I mount an elbow on the inlet inside the skimmer to facilitate swirling?

(4) If I mount an elbow, should I point it horizontally, slightly up, or slightly down?

(5) For the removable skimmate cup, will a slip-fit seal sufficiantly to keep skimmate foam from leaking between the cup neck and the half coupling?

[XORRO]

an acrylic "main/reaction" tube would be cool to see the bubles but ,I think an acrylic collar or the tube that connects the reaction chamber and the cup would be more bennifical for tuning the skimmate output. The way you have it now it will be difficult to change that ,and the addidion of valves on the input and output would allow you additional control if your air pump does not offer that. Also ,are you planning on using a powerhead to bring water in/out or just the air pump for movement? An on what size tank is this going to be implemented? {3} I think the elbow should be pointed slightly down if you plan to go that route but I would also try a 45 to see what the effects are if any. I would also mount some sort of filtration bag on the end and if in a sump ,submerge it to help alleviate and remaing micro bubbles.

[Mr. Fosi]

...I think an acrylic collar or the tube that connects the reaction chamber and the cup would be more bennifical for tuning the skimmate output.

 

I agree, but cost is an issue. If I buy acrylic tube I will double the cost. As it is, I can tune it by seeing what kind of skimmate it produces.

 

...the addidion of valves on the input and output would allow you additional control if your air pump does not offer that.

 

What if I control only the output? The waterpump I will be using (minijet 404) has its own flow control, so couldn't I control the water leaving the skimmer in order to manipulate in-skimmer water height? One of my airpumps has a rheostat control and the others can be controlled by simple Lee's in-line valves.

 

Also ,are you planning on using a powerhead to bring water in/out or just the air pump for movement?

 

Water will be actively pumped in by the minijet, making this is counter-current skimmer.

 

An on what size tank is this going to be implemented?

 

Initially, this will be used on a 5g bucket containing uncured live rock. After the rock has cured, I may use this on my 5.5g AGA.

 

...but I would also try a 45 to see what the effects are if any.

 

What do you mean by 'a 45'? Do you mean a 45 degree elbow?

 

I would also mount some sort of filtration bag on the end and if in a sump ,submerge it to help alleviate and remaing micro bubbles.

 

So you believe that there will be residual microbubbles even with a throughput around 80gph. Perhaps I could build a bubble trap box on the output.

 

Anyone have any answers to the rest of the queastions?

[RP Beesh]

y not do a venture skimmer?

[XORRO]

Well I may have found an answer to the acrylic neck if your interested. Depending on what diameter your using, you may be able to use one of those gravel filter tubes because they are cheap and clear ,but you would have to make sure they are the right diameter for your exsisting project. They are cheap and available at wallmart and petco ect... Yes you could probably get away with only one valve on the out put and yes I meant a 45 degree angle to possibly soften the angle and create more swirl in the reaction chamber. I do believe there may be microbubles initally but you have a decent height and a low flow rate so it could go either way. More pics once your further along would probably help.

[Mr. Fosi]

y not do a venture skimmer?

 

While there are destinct advantages to doing a veturi skimmer (such as low maintenance), I am not sure that I will be able to get fine enough bubbles with the low flow that I am planning to use. If anyone out there can assure me that I will be able to get good air injection with a flow rate around 80gph, I'll try it.

 

Well I may have found an answer to the acrylic neck if your interested. Depending on what diameter your using, you may be able to use one of those gravel filter tubes because they are cheap and clear ,but you would have to make sure they are the right diameter for your exsisting project.

 

I have a buch of these sitting around, so they were the first thing that I thought of. They are not nearly the right size, however. In addition to their wrong size and the difficulty I would have gluing them to PVC, it would also be hard to fit them into the holes that I have already cut into the caps.

 

...yes I meant a 45 degree angle to possibly soften the angle and create more swirl in the reaction chamber.

 

I thought a 90 degree angle directed over the inner surface would create more swirl, until I drew this pic to illustrate what you were suggesting.

 

 

More pics once your further along would probably help.

 

More pics will be forthcoming. I will get the 1.5" coupling and cut it in half today, then I wil post pics of it glued onto the caps.

 

We have dealt superficially with microbubbles, but that still leaves initial questions 1, 2, & 5 to be answered.

[Mr. Fosi]

Initial questions 1, 2, & 5 have yet to be addressed, but I am moving forward. I was contacted yesterday by Beth at Dr. Mac's who told me that my rock had shipped, so this thing needs to be completed and tested tonight.

 

Here is the latest barrage of pics:

 

We'll begin with an exploded view of the skimmer parts.

 

 

 

These pictures show a 4" cap into which a hole has been cut and half of a 1.5" coupling has been glued with PVC/CPVC multipurpose solvent glue. There are two of these: one for the top of the skimmer body and one for the bottom of the collection cup. The coupling halves are a tight fit around the 1.5" neck pipe and should seal well w/o glue, allowing them to be removed.

 

 

These pictures show the 3" piece of 4" pipe that forms the collection cup wall and the assembled collection cup, inner and outer. The also show the quality of the joints that will butt up against the neck pipe.

 

 

 

Here are closeups of the 1/2" outlet and 3/4" inlets. I drilled these holes, then sanded them until I could hammer the fittings in. They have been sealed w/glue.

 

 

 

This is the body, neck, and cup assembled.

 

 

And finally, here are two views including the 1/2" outlet pipe. None of the outlet has yet been glued.

 

 

 

Things yet to be done:

 

- Figure out how I am going to connect my water pump to the inlet

- Figure out where to run rigid air tubing and at what depth to hang the stone.

- Drill a drain for the cup

- Make a lid for the cup

- Glue all permanent joints and seal ones who's integrity is in question (such as the coupling/cap butt joints).

[Blind Tree Frog]

Any reason you are making it counter current and no co current? I wouldn't think there would be a heavy enough load for anything too facny skimmer wise in just a live rock tank, but I could be wrong.

[Mr. Fosi]

Any reason you are making it counter current and no co current?

 

I thought about doing a co-current like I have seen recently here in the DIY section, but I put that idea aside b/c I would eventually like to upgrade to a slightly larger tank and encorporate some corals. Also, I like the out-of-the-tank style, given that I have a very limited in-tank area and I don't want to make any more cuts or holes in my hood.

 

I wouldn't think there would be a heavy enough load for anything too facny skimmer wise in just a live rock tank, but I could be wrong.

 

You are right about that. I am certain that a skimmer of this size (close to 20% of the tank volume) is overkill for the 5.5g AGA FOWLR.

 

I think that overkill for the 5.5g is just the right size to cure the rock that I ordered. I expect the 4lbs of Pacific Aquaculture rock to be in bad shape (really uncured and stinky) and rather than prolong the curing time with a small airlift tube co-current skimmer, I think that going the 'Tim Allen' route will work well.

 

Any suggestions regarding my 'to do list' or comments on questions 1, 2, or 5?

 

 

(1) Do I need back pressure to eliminate micro bubbles?

(2) Will 3/4" inlet to 1/2" outlet create enough back pressure to eliminate microbubbles?

(5) For the removable skimmate cup, will a slip-fit seal sufficiantly to keep skimmate foam from leaking between the cup neck and the half coupling?

[Blind Tree Frog]

Regarding your questions, I'm just bull######## answers, so take them with a grain of salt:

 

1) Bubbles would need to settle out. This would take slower moving if not standing water. Back pressure might slow the flow enough to help

 

2) Smaller pipes would increase water velocity. Faster velocity I would think would trap bubbles.

 

3) If not, teflon tape is your friend.

 

 

Why not put a small cup with a few inch rise at the bottom of your skimmer. The air stone would sit in the cup and the sides of the cup would make sure that the bubbles are introduced above the level of the outlet. I would think that that would prevent some of your microbubble fears (or at least reduce them)

[Mr. Fosi]

Why not put a small cup with a few inch rise at the bottom of your skimmer... I would think that that would prevent some of your microbubble fears (or at least reduce them)

 

That's not a bad idea, but wouldn't it be simpler to just hang the stone with the rigid air tube wherever I need it? If I put such a baffle in it, it'd make the bottom of the skimmer harder to clean.

 

I wonder if an anti bubble box (like on a turbo floater) would be useful...

 

Any other comments or suggestions? I am not going to glue it all together until tonite, so get them in while you can!

[Blind Tree Frog]

Psh, fine if you want to do it the easy way

 

:-P

[Mr. Fosi]

I tested it last night.

 

I couldn't get an acceptable amount of bubbles until I attached TWO airpumps to the coralife wood airstone. When I hooked up the two airpumps I got a huge amount of fine bubbles leading to a thick foam within about 5 min. I played around with the water flow in and out of the skimmer and was able to get it foaming where I wanted it.

 

I would have let it run all night, but it sprung a couple leaks from two of my teflon-taped joints. I glued the joints, then set it running this morning. I was in a hurry, so I wasn't able to tune it like I did last night.

 

I'll have an update with pictures after work.

 

My Pacific East Aquaculture rock came in today and I have a few pics of how it arrived and I'll post some more detailed ones after work.

 

It doesn't look or smell like uncured rock. In fact, it smells quite rosey and looks pretty clean. I am not going to rush to any judgements yet, but I really hope that it is uncured since that is what I specifically requested.

 

 

 

If it turns out not to be uncured rock, I am going to complain. The whole reason that I ordered the rock was to get some neat critters.

[Mr. Fosi]

Well, here's a picture of the rock out of the bag.

 

 

 

 

And here is a picture of my gettorigged test. I have the water and rock in one bucket and the skimmer in another, just in case it leaks. The airpump sitting on the collection cup is holding the airline so the rigid tubing doesn't shoot back out the body.

 

 

 

 

Here is a picture of the skimmate produced in 6hrs. Its a little watery b/c I had been playing with it and overflowed the neck a couple times.

 

 

 

 

So far I have seen zero microbubbles and I am running it just below 100gph. I don't have an exact output figure, b/c I never tested the pump output at the setting I have it on.

 

As it is, I don't think that the rock is uncured, so I probably won't have to leave it in the water very long before moving it to my tank.

 

I am going to do a couple of other mods to the skimmer when it is done with the rock:

 

(1) Attach a flat bottom so it can stand up straight.

(2) Glue the hard plumbing or completely soft-plumb the output.

(3) Make a cap for the collection cup.

(4) Elongate the collection cup wall.

(5) Find a way to firmly, but not permanantly, mount the airhose so it stays at the correct depth.

[RP Beesh]

Regarding your questions, I'm just bull######## answers, so take them with a grain of salt:

 

1) Bubbles would need to settle out. This would take slower moving if not standing water. Back pressure might slow the flow enough to help

 

2) Smaller pipes would increase water velocity. Faster velocity I would think would trap bubbles.

 

3) If not, teflon tape is your friend.

Why not put a small cup with a few inch rise at the bottom of your skimmer. The air stone would sit in the cup and the sides of the cup would make sure that the bubbles are introduced above the level of the outlet. I would think that that would prevent some of your microbubble fears (or at least reduce them)

#2 is wrong the bigger the pipes the higher the velocity of water travel through it.

[Mr. Fosi]

#2 is wrong the bigger the pipes the higher the velocity of water travel through it.

 

Perhaps he was thinking of the Bernoulli Principle?

 

I tinkered with the skimmer for all of last night b/c the bubble/water level kept fluctuating. I kept messing with the air input, the water input/output but it just wouldn't stay at a constant level.

 

I had the output almost completely closed and then it hit me: "Check the pump intake, dummy!"

 

I have had the little minijet 404 that I am using to power this monster for years. My one gripe about it is that the intake clogs WAY to easily. In this case, there was a compacted wad of decaying chaeto stuck in the intake grill. Once I cleared that obstruction and got it out of the bucket, the bubbles stayed where I wanted them. I let the skimmer run all night with a 9w 6500K light on.

 

Last night, the water was so cloudy that you could hardly see the rock and here is a picture of the rock as of this morning (I had just turkey basted the rock).

 

 

 

 

I am sorely tempted to take the smallest piece of rock out and put it in my tank tonight, but I don't think that would be a good idea. Before I make a final decision I am going to have one of the LFSs test the water from the bucket. Only if the NH3 level is undetectable am I going to do it.

[neanderthalman]

#2 is wrong the bigger the pipes the higher the velocity of water travel through it.

 

 

Umm....no.....assuming that the flow rate of the water, in gph, is the same for both pipes, the smaller pipe will have the water moving at a higher linear velocity. Here's the math.

 

If you have a pipe of 1cm diameter, you'll have a cross sectional area of about 3.14 cm^2. This is easier in metric, so I apologize. 100gph is equal to 378L/h, or 105 mL/s. In the metric system, one mL is equal to one cm^3. So...105mL of water would fill a section of pipe 105/3.14 = 33.37cm, a little more than a foot. Since we have this volume of water moving through the end of the pipe every second, the water must be moving at a linear velocity of 33.37cm/s, or 0.33m/s (~1 foot per second).

 

Lets try it again with a larger diameter pipe, lets go with 10cm.

 

Cross sectional area - 314.5 cm^2

Volume of flow - 105 mL/s - same as before

105mL fills a section of pipe 0.33cm long - a little more than 1/8"

That means that, for 105mL/s to flow out the end of the pipe, the linear velocity has to be 3.3mm/S, or 0.0033 m/s, or 1/8" per second.

 

A fatter pipe has a slower linear velocity, but decreases head loss.

 

[/Lesson]

[Mr. Fosi]

This is easier in metric, so I apologize.

 

Don't apologize. Every bit of science and most of the engineering that makes people's lives easier is investigated, reporteded, and executed using the metric system.

 

[/backup]

 

What do you think of the design? You were have had good ideas in the past, perhaps you will share a few here?

[neanderthalman]

Let's see what I can come up with I have no experience with skimmers, so I'll admit that my suggestions are theoretical.

 

For Question 1 / 2, about the back pressure. I don't think back pressure has much effect on whether or not the bubbles make it out of the skimmer. Back pressure will reduce the flow rate in the skimmer, reducing the number of microbubbles escaping as a secondary effect.

 

Try having the skimmer output cascade onto a sponge. I think it should eliminate any microbubbles that do manage to escape. As with any other mechanical filtration, replace sponge weekly

 

I think a slip seal would be enough to keep the skimmate in. All of the commercial skimmers must have one in order to be adjustable. The skimmate isn't under any sort of pressure either.

[Mr. Fosi]

Makes sense, as usual.

 

Hows about these?

 

- Attach a flat bottom so it can stand up straight.

- Find a way to firmly, but not permanantly, mount the airhose so it stays at the correct depth.

 

I was thinking of gluing a PCV toilet flange to the bottom to make it flat, but I am looking for other ideas that may be more clever.

 

As for the airhose/rigid tubing, I was thinking of plumbing it through the neck or the top cap of the skimmer body. If I do that, I will have to worry about seal and it will be more difficult to change the airstone... I'm hoping for a better solution than either drilling another hole, or putting something on top of the skimmer to hold the hose in place.

[neanderthalman]

For the airhose, look at this picture....

 

 

Cut a notch slightly smaller than the airline tubing into the inner pipe, right where the airline is entering in that pic. Jam the airline into the notch. It'll hold it in place without pinching it off.

 

Flat bottom....hmm..... How about a PVC ring, cut from the same size pipe as the main reaction chamber. Glue it to the bottom cap, and voila, flat bottom. It's not a very wide bottom though, but it would use supplies and waste PVC that I think you'd already have on hand.

[Mr. Fosi]

See? I knew you'd come up with good stuff.

 

I'm going to do both of the suggestions you have made.

[Mr. Fosi]

I visited one of the newer LFSs last night.

 

The guy who runs it had been stringing me along for the last month and a half with regards to LR. He said he was going to get some in, but it was one problem after another.

 

Well, when I stopped in last night and discovered that he had recieved 100lbs from some place in FL. The rock is extremely raw and covered in neat/dead things. It is just the sort of stuff that I was hoping to get from Dr. Mac, so I picked up 1.5lbs of it for $7.00/lb. I also got some good skimmer pointers, which I will detail below.

 

It is 'aquacultured' rock, which I haven't had good experience with in the past, but this stuff is BOSS. It has all kinds of macros and coralines on it, a couple tube worms, and some other stuff. Few of the bigger pieces had small plate corals and zoanthids on them. I guess the supplier pumps seawater through fishery-style runways that are filled with aragonite rock. Whenever they get an order for rock, they pull it out and ship it ASAP. It is only in the box for around 12hrs.

 

I was so excited about it last night, that I forgot to snap a picture; I will get one or two tonite.

 

This is a picture of the rock as it was this morning (day 3). The water has completely cleared and still smells rosey.

 

 

 

 

And here is a pic of a very awsome mod that I made to my origional skimmer design.

 

 

 

 

I swapped out the origional oulet pipe for one that is 6-8" taller and added a breather tube to it. When I visited the LFS guy, I talked to him for a couple min about the 6' tall DIY skimmer that he has skimming his 800g common system (he has three common systems in the store). In particular, I asked him why his outflow pipe was so high and why he had a breather tube on it.

 

What he told me made me wonder what the heck I was thinking when I drew up the origional design: The height of the outlet is the level to which the water will rise in the skimmer, duh! Also, the breather allows the outlet to suck in air and keep from choking, allowing the level in the skimmer to remain constant.

 

So I went to the hardware store, picked up some fittings, and swapped out the outlet pipe: VOILA! The level in the skimmer remains constant regarless of whether the pump is a little clogged. In return for this miracle, I now have a gurgling sound coming from the breather hole, but I will remedy that tonight by drilling a bigger hole and lightly jamming some filter floss into it.

 

He also said that he added a lid to his skimmer cup b/c the skimmate was drying out and not really coming out the the water, so I added a lid to mine as well. The result? Nice, thick foam this morning. I will snap pictures of what it looks like tonite.

 

EDIT: N-Man's mods = Perfection

[GrizzleBee's]

Wow, this skimmer is sweet. You could even put a gate/ball-valve thing on the outlet, to raise the water level in the skimmer body in case you needed to.

[Mr. Fosi]

Yeah, I have a ball valve from a magnum canister filter on the oulet. It has helped to tune it in very small amounts, but it didn't really help until I swapped the outlet pipe.

 

Not bad for less than $15.