Octopus Skimmer Mods

[skwirl]

what do you use to ream out the inside?

[davidabrown66]

Originally posted by JCTewks
I really don't see why you shouldn't get 38SCFH out of an OTP3000. I'm getting 20SCFH out of an OTP1000 that is rated at 1/3 the output of the 3000. Rich Conley had at one point an OTP3000 pulling 50+SCFH. He couldn't even use that on his skimmer as it was way too much air for the DNW200.

Are you guys reaming out the inside of the volute at all? or just tweaking the impeller and venturi?

I've ground down the edge of the volute where the water leaves the pump which did give me 2 to 3 SCFH. I've done the gasket mod, the reaming of the output plumbing and opened up all plumbing by reaming with 5/8" spade bit including the pump output and restrictive 90 elbow. I've got 3 layers of thick mesh, and drilled out the venturi all different ways using 3 different stock venturi's. I now have a 3/8" barbed fitting tapped in where the stock air nipple used to be. I've tried RO line and a JG fitting, but it didn't make a difference. I've tried drilling straight down vs keeping the 90 in the airway for the venturi, and just opening up the airway to the size of RO line, but didn't help. I know it's hard to believe, but either the pump has changed since then or my meter is wrong. I'm open to other mods, and I'm actually hoping there's more to be done on the volute if I've not done everything I can there.

[davidabrown66]

Originally posted by skwirl
what do you use to ream out the inside?

5/8" spade bit

[davidabrown66]

I'm reposting this here to see if anyone can help. I have a Gen-x 4100 with SP4 from ER as a replacement for the OTP-3000 for my DNW-200. I also have the volute and venturi for the Gen-x from ER. I first tried all the components together a couple of days ago, and my air meter said 18 SCFH. I was expecting better.

So, last PM I tried 3 layers of mesh after snipping off all the small nw's of the ER impeller and leaving the larger ones to keep the mesh from slipping. I'm now getting 22 SCFH, but I think the pump is cavitating, b/c the output is weak, and pump is extremely noisy.

Overall, very disappointing from what I thought was going to be 900 LPH stock using the ER NW, volute and venturi. I'll have to cut back on the mesh, and see if I can improve the #'s. I did try and restrict the air input by using ro line inserted into the 3/8" airline, but that didn't do anything. The pump is sitting in a 5 gal bucket of saltwater without any plumbing attached, and the performance doesn't even compare to what I'm getting with my OTP 3000. So far this is a very expensive dud of a mod. I must be doing something wrong, b/c I've heard over an over again that the gen-x 4100 is supposed to rock. I'm going to also try and make my own venturi from 1" pvc to 3/4" back to 1" again, and insert a JG fitting at the 3/4" restriction just before it transitions back to 1", and then grind down the edges of the 3/4" plumbing so it transitions well.

As a side note, I bought the ER volute that has the venturi already attached to it. It looks like the venturi might have been put on wrong, b/c the air intake is located closer to the input of the venturi rather than the input to the volute, but it's already glued together. Not sure if this is right.

Anyway, I have a stock volute which is the same as the other one, and I'll try my own venturi to see what I can do.

Could my SCFH meter be off? B/c my numbers should be higher for my OTP-3000 as well. It just seems strange that I can't get more than 500 LPH of air out of a Gen-x 4100 with ER SP4. Any ideas?

[JCTewks]

Originally posted by davidabrown66
I've ground down the edge of the volute where the water leaves the pump which did give me 2 to 3 SCFH. I've done the gasket mod, the reaming of the output plumbing and opened up all plumbing by reaming with 5/8" spade bit including the pump output and restrictive 90 elbow. I've got 3 layers of thick mesh, and drilled out the venturi all different ways using 3 different stock venturi's. I now have a 3/8" barbed fitting tapped in where the stock air nipple used to be. I've tried RO line and a JG fitting, but it didn't make a difference. I've tried drilling straight down vs keeping the 90 in the airway for the venturi, and just opening up the airway to the size of RO line, but didn't help. I know it's hard to believe, but either the pump has changed since then or my meter is wrong. I'm open to other mods, and I'm actually hoping there's more to be done on the volute if I've not done everything I can there.

I removed all of the material around the inside of the volute...that little 1/16" thick wall that covers the whole inside of the volute about 1/2" high. i also thinned down the volute cover just a bit(about 1/32") you just have to be really careful not to go through the plastic or you're screwed and will have to get a new volute cover. My venturi is the standard 90 that I reamed out to take a 1/4" ID barb connector. the connector is a barb x barb. I smoothed the end that goes inside the 90 so that all of the barbs are gone, and cut a steep angle. I cut the barb so that it went all the way in and touched the other side of the 90. I tried it shorter and the numbers weren't nearly as good. I'll try and get some pictures of the inside of the volute next time I clean the skimmer.

Here is my DNW 110. the air is actually rolled back to about 15SCFH to keep from overflowing the skimmer.

[JCTewks]

Originally posted by davidabrown66
Could my SCFH meter be off? B/c my numbers should be higher for my OTP-3000 as well. It just seems strange that I can't get more than 500 LPH of air out of a Gen-x 4100 with ER SP4. Any ideas?

What is the ID of the fitting on your meter? also, what model meter do you have?

[outy]

hes got the rma 7 like mine.

[o2fly]

Cool thread, just bought a DNW150 and planning on modding pretty much every thing , Has any 1 built a self cleaning head for the RO Skimmers?

[davidabrown66]

Originally posted by JCTewks
What is the ID of the fitting on your meter? also, what model meter do you have?

I use a 3/8" by 1/8" threaded hose barb for the venturi input and the meter, and I can fit RO line into the hose barb so the internal diameter is 1/4". The meter is a RMA-7 and is 5" tall. It measures SCFH, and if I remember correctly I would multiply SCFH x .472 x 60 to get LPH.

[impur]

Just got my airflow meter, RMA-22. Need to pickup a few fittings to adapt to the airline. I'll report what i'm getting this weekend.

[outy]

impur spi fi way to go lol been in finance, closed but theres to much cash on the line where im at lol

bought time you got your meter youve been modded for quite a while

[impur]

Yah, but 25mil at 30% is a nice return!!!

I hear ya, i've been wanting to get this thing fine tuned for awhile. Nows my chance

[JCTewks]

Originally posted by davidabrown66
I use a 3/8" by 1/8" threaded hose barb for the venturi input and the meter, and I can fit RO line into the hose barb so the internal diameter is 1/4". The meter is a RMA-7 and is 5" tall. It measures SCFH, and if I remember correctly I would multiply SCFH x .472 x 60 to get LPH.

I think the size of your venturi os the biggest reason you aren't getting impressive numbers. You should be using 1/4" ID venturi air inlet, as well as on the meter. Those little 1/8" fittings on the factory venturi are poor at getting large volumes of air in. Try making a venturi with 1/4"ID barb and hose and i bet you're numbers will go way up. BTW the meter i have is ithink a RMB-55...it is about 10"tall and reads to 50SCFH/ 20LPM...it is a dual scale. was about $40 shipping and all. Let us know how it goes with the new venturi. I'm even thinking about trying a venturi with 3/8"ID tube and see if I can get one of these to even start cavitating....haven't been anle to yet

[JCTewks]

Sorry david...i think i misread your post...are you using 1/8, 0r 3/8 line?? my meter has a 3/8" threaded input on it, i think i'm confused. :l

[outy]

maybe davids venturi is to large im pulling 36scfh with 3/16 id following roland j,s directions with the jg fitting and not drilling through the 90. i think roland said that was good enough to get you into the mid 40,s [scfh]

ya that 1/8" is confusing.

[impur]

Whats the math to convert lpm to scfh?

[impur]

Nevermind, found it.

If anyone wants to know, to convert lpm to scfh multiply lpm X 2.11896 = scfh

http://www.thermadyne.com/victor/lit...rs_General.pdf

I'm getting 23scfh, or 11 lpm thru my airflow meter. Pretty good, i'm going to do some more messing around with it today.

[skatezen]

I got my DNW-200 in last week and I was pretty happy with its performance. This weekend I did the o ring mod, the volute mod, the mesh mod, and the Venturi - RO line mod. All I have to say is HOLY CRAP!!!! This thing is a beast!!!

I have to admit, I did screw up the volute mod and I actually shaved off to much material with the 11/16" cone abrasive. I don't thing that I removed to much material, just that it got so hot it melted and twisted off. I'm talking about the piece that held on the black screw with attached the the union with the 90 to the pump. I was able to fix this with some marine epoxy. I once this skimmer is settled in I think I will be more than happy with it as reef investment.

[luke33]

Hey guys, just wanted to share this chart with you.

http://www.randystacye.com/images/di...Conversion.xls

[outy]

thanks thats pretty cool

[cee]

OK, now I'm up to the following:

1) 4 layers of Enkamat on the NW after removing 1 layer and half the needles on the 2nd. Pulled it all together by weaving fishing line around and doesn't appear to be rubbing anywhere, but time will tell.

2) Modified the venturi significantly. Added a 3/8" JG fitting to replace the stock barb fitting. Then I got creative. I extended the end of the 90 degree where it comes out near the washer another 1/2" or so with reamed out rigid airline tubing, so now it "exhausts" closer to the center of the water column in the venturi. Also, to maintain the venturi effect longer and get it closer to the input of the pump, I added about 3/4" of CPVC, 1/2" coupler, with the edge dremeled out to clear the rigid airline tubing. It fits tight against the ID of the rubber washer and doesn't need to be glued in and has the same ID as the stock venturi.

This thing is really pulling some air now, so much so I'm worried about overflows after it breaks in. It's probably pulling air comparable to my MRC Beckett skimmer. I don't have a flowmeter, but I'll try and get pics in a few days.

[skey44]

what is the problem if the pump seems to be cavitating from the bubbles in the skimmer body? i've added two layers of gg and one thick layer of enkamat inbetween pulled tight with zip ties. i have removed all but the bottom layer of pins on the impeller and have reduced its size and weight signigicantly. did i do too much, and its trying to pull too much air and not enough water?

[outy]

what have you done to the venturi.

what else have you done

what kind of skimmer do you have

[carlos_fb]

As I mentioned before, I could not get my NW-150 to work properly with the gate valve and even without it, the skimmer is very sensitive to any changes in the water level. I am thinking on getting a recirculating 150.

- Any opinions about it?
- Any suggested mods?
- What is the best pump for it?

[impur]

I played with the venturi a little, went to a slightly larger ID tubing for the air and now i'm only getting about 7lpm.