Advice on DIY skimmer design

Reefer Addict · 07-15-2003, 02:33 PM

Well, I've been needing a new PVC project to keep me busy, so I decided that I need a better skimmer to replace my venerable Seaclone 150.
At first I was looking into eductor driven designs, but decided that a standard venturi driven design would be a better option.

I spent most of yesterday evening modifying Geoff's skimmer design a bit, and the attached picture shows what I have come up with.

The picture should tell most of the story, but the one part I'm uncertain is the way I have the venturi right before the pipe enters the skimmer body.
I wanted to be able to adjust the waterflow initially, and then adjust the airflow once the water has been dialed in.

I'm pretty sure it should work, and it'll double as a siphon break if the power should shut off for some reason, but it's nice to have second opinions.

I also extended the feed tube down into the inside skimmer tube (Geoff's design ends at the elbow) so that it wouldn't interfere with the exiting bubbles as much, though I'm not sure if that is needed either.

I'm planning on using 3/4" PVC for the feedline and 1" for the return line so I can push more water through the skimmer if I need to.

The design isn't to scale or even sized accurately for that matter, but it was just a rough idea on how I was going to go about building it... I find that whenever I set my plans in stone they always end up changing during the construction phase to compensate for unknown variables.

Anyway, any advice I can get on this will be appreciated.

Thanks.

David.

P.S. The extra 't' fitting on the return line toward the top of the skimmer body is for support only... it'll just be glued to the outside of the skimmer.

Geoff · 07-15-2003, 03:43 PM

looks good!!

the only thing i noticed is that you do not have a way to adjust the height of the water inside the skimmer. i have a couple of slide expansion joints on the outlet to be able to adjust the water height inside the skimmer.

i actually do have the feed line going almost to the bottom of the skimmer. i will double check that on the site, apparantly i am not clear on that. i did it that way to increase the contact time with the water.

the thing i wish i could do to make mine better, but i just do not have the room, would be to make the skimmer out of 6" PVC instead of 4" that would really increase the contact time with the water.

i like where the venturi is, i wanted to do that, but i just did not have the room. if you want to adjust the water flow the closer the ball valve is to the venturi valve the better. it keeps the velocity of the water as high as possible when it hits the venturi valve.

i like it!

G~

Reefer Addict · 07-15-2003, 05:03 PM

Thanks for the reply Geoff.

And also thanks for the inspiration...

Anyway, I'm a visual person, so I quickly read over the construction plans for the skimmer, and went straight to the pictures. This is the picture that made me think that the tube didn't go all the way to the bottom (I just assumed you used the velocity of the water to push it to the bottom):
(I'll continue in the next post)

P.S. As an aside... it really tripped me out when I opened this image in Photoshop to resize it and it asked if I wished to convert the ColorSync profile... then I remembered that you're a Mac user.

Reefer Addict · 07-15-2003, 05:11 PM

(continued)

I also took some of your advice into consideration, and modified the schematic a bit. I had planned to use the ball-valve on the feedline to control the height of the water... I figured that with a 1" drain the Mag7 will provide more than enough flow to overwhelm it's draining capacity, so I'd be able to get the height I wanted by controlling how much water I pumped into the skimmer.
My thinking behind this was that I have a Mag5 return pump at a 6' head running my sump return, and I still need dual 3/4" overflow tubes to get enough drain or the height of the water goes up in the tank... I just transferred this over to the skimmer, figuring it would work as well.

Anyway, here's the changes I've made so far. I moved the venturi so that it sits right past the ball valve. I'll probably use a guest 90-degree elbow quick-release fitting screwed into a 3/4" flange. I also extended the inside feed tube to the bottom of the skimmer. I probably won't make it as long as I have it in the schematic, but it gives me a rough idea of how much PVC I'm gonna need.

I'll recheck your site on the slip fitting for water height adjustment in case what I plan on doing doesn't work.

Reefer Addict · 07-15-2003, 06:27 PM

Well, I did a bit more thorough read of the skimmer construction instructions and now see that you do mention the 32" length of 1/2" PVC...
I was just too impatient.

I'll also look into using a 1/2" feedline inside the skimmer body... probably use a 3/4"-1/2" elbow that way I get maximum clearance for the water coming back up from the pipe.

I also see what you mean about water height control... I had planned on using the pump to do the job but I may get too much flow through the skimmer... I wonder if adding a ball valve inline with the return line would do the job?

Thanks again for your input.

Geoff · 07-15-2003, 11:35 PM

the venturi valve really cuts the flow down from the pump. i am using a mag 7 and i do not think i am getting more than about 300gph out of the skimmer! those venturi valves produce a lot of back pressure on the pumps. this is why the slide adjustment on the output is necessary. i am pretty sure you will not reach full capacity on the outlet with a mag 5 throught the venturi. you may if you used an airstone, but not with a venturi.

using a ball valve in line would prolly work fine. a lot of high end skimmers use this approach. if you go this route then you may want to plumb directly into the sump. i think it will give you better control. the problem would be depending on the size of the skimmer the equalization height of the water if the power goes out could be to much for the sump to handle. also if you go this approach i would suggest a gate valve instead. you have finer adjustments.

going from 3/4 to 1/2 on the feedpipe, i think will not make that big of a difference. the real difference would be if you could make the main body out of larger pvc. this outer sleave is where the greatest contact time can occur. this is where the slower the velocity (not total flow) of the water can add the greatest contact time and allow more of the lighter bubbles to get up to the top of the skimmer for export.

G~

P.S.-i forgot i used photoshop to do the images.

Reefer Addict · 07-16-2003, 02:44 AM

I was actually going to use a Mag7 on the skimmer... I read back over my post and I see where I led you astray... my bad... sorry for the confusion.

One question I have regarding the venturi slowing down the waterflow is that since my venturi is a lot closer to where it enters the skimmer wouldn't I be able to get a bit higher waterflow? I kinda thought that since I'm pumping water up to the ball valve the air shouldn't affect the flowrate as much since it comes further down the line. In your design the venturi is plumbed next to the pump so it pumps the air/water mixture pretty much over the full length.
It's been a long time since I got my degree in fluid dynamics (not!) so I'm a little fuzzy...

Thanks again for your input.

David.

Geoff · 07-16-2003, 09:40 AM

i do not think it will effect it that much where the venturi is, but hey i could be wrong on this though. it is PVC so if it does not work as planned, hey it is on to version 2.

i like messing with skimmers. it is $25 bucks worth of PVC each try.

G~

Reefer Addict · 07-16-2003, 12:35 PM

That's the great thing about PVC... cheap and plentiful.

Thanks for all your help Geoff... I'm probably going to get started on it this weekend.

RA

Reefer Addict · 07-17-2003, 11:55 PM

Well, here's the 'finalized' (on paper anyway) design that I'll be working from as I build my skimmer...
I priced out materials today and it should cost right around $70 for everything but the Mag7 pump (another $55)

I plan on taking some pictures during the construction, and I'll post some pictures of it when I finish.

The little blue rectangles on the skimmer body and the skimmate collector will be 1/4" acrylic viewing holes so I can see what's going on inside.

wanareef · 07-18-2003, 04:12 AM

reeferadddict

On that waste collector, I would add a auto-cut-off. Basically it's a ping-pong ball in a tube with a hole at the top (vent). When the gunk gets too high, and raises the ball it will stop the foam. Checkout Snailman's site. I have one on mine and (on everyone I have made), where it vents out- the "stink" has to go through some carbon before it goes into the air (living room). Skimmate= stink mate

hth

Geoff · 07-18-2003, 09:36 AM

Looks Great!!

why 1/4" acrylic? if you use 1/8" you may be able to bend it around the PVC and make a bigger view port. i have found that the PVC cement does a decent job of attaching PVC to acrylic. i would try on a scrap piece just to make sure it can handle the extra force of the bend.

that ping-pong ball sounds like a interesting idea.

G~

Reefer Addict · 07-18-2003, 12:42 PM

Thanks for the advice there wanareef, I'll look into both your suggestions. Snailman's skimmers were actually the first I checked out when I decided to DIY my own.

Geoff,
I was going to use 1/4" so I'd have enough of an edge to get a good glue hold between the PVC and acrylic... I was just gonna slice out about a 1/2" piece in the PVC and glue the window into it...
I find that I usually change my mind several times during the construction phase of whatever it is I'm 'backyard engineering' so nothing's really set in stone until I finish.

I'll keep you suggestion in mind also... I have some extra scraps of 1/8" acrylic laying around that would probably work.

Thanks again guys for the input.

David.

Geoff · 07-18-2003, 12:46 PM

Quote:

Originally posted by Reefer Addict

I find that I usually change my mind several times during the construction phase of whatever it is I'm 'backyard engineering' so nothing's really set in stone until I finish.

this is why i am so bad at taking pics of my projects. i find that the pics are showing things i have changed later, so they are now useless.

G~

Reefer Addict · 07-29-2003, 08:23 PM

Well, I've finally been able to work on the skimmer the past couple of days, and attached below is the final product.
I haven't gotten a chance to wet test it yet, but I have to wait for the cement and epoxy to cure overnight. I threw caution into the wind and just glued it right off the bat... I'm confident enough in the theory behind it that I'm almost 99% sure I shouldn't have problems.
One major design change I made in the process was to cut down the center tube inside the skimmer to about 14". I got to looking at the design, and a shorter inside tube gives more contact time over a larger area.
I'm almost embarassed to say how I came about this 'revelation', but I was looking at my seaclone 150 in operation and watched how the bubbles dissipated once they exited the feed tube... then I remembered that the biggest gripe about the seaclone is too little contact time and that the cure is to shorten the riser. I looked at the riser in my design and it went almost to the top of the skimmer... aha!
The way it is designed now, the inside tube just keeps the air/water mixture from being directly ejected through the drain and feeds it back into an upward trajectory. I left about 14" of drain space so that any stray microbubbles have a chance to rise back up into the column before getting sucked back into the sump.
I'll post again once I get it tested and installed.

I've named my skimmer "Monstro and Mini-me"

It stands about 45" tall.