What do I gain from extending the neck of my skimmer

I have a SRO 3000INT Skimmer on my 180 setup. Total system volume is in the 220 range with 13 fish. I am considering adding a 3" neck extension to it as I have read it gives more dwell time for the water. What am I really gaining?

 

Well at the very least it will give you the ability to have dryer skimmate. I guess the dwell time comment makes some sense but to me the bigger benefit is the skimmate adjustment as there have been many times I've wished for an extension for that.

matt

 

To me, it seems like an add on for a improperly sized, or improperly designed skimmer. Nothing is free.

If you buy the right skimmer for your application, then you will have all the adjustment you need, and it will give you all you need.

So now you move up say and it is not doing enough. OK, so stack the neck... you can lower the skimmer in the sump, put through more water, and get proper skimmate. But you are just stuffing more air and water through a body that was not designed for it. And to me, more "dwell time" is dubious at best. More water through at a faster speed down not equal greater retention "dwell" time. A larger body with the SAME throughput equals more dwell time... or of course same volume with less through put equals more.

AFAIK, dwell time is overrated. Not really of course, it is a legit factor. But a properly sized skimmer will be a little over what you need. It will do all you need. I like 1.5X tank. 100g tank skimmer rated for 150. So even if you do increase dwell time, and you do increase performance... well now it will do 180... but you didn't need the 30g improvement in the first place, and a skimmer is only going to remove what is there.

Needle wheel skimmers work through shear force of shredding bubbles to really fine size to increase contact surface area. A stable foam head will allow the bubbles (surface area with bound DOCs) to rise and transport DOCs to the top and over the edge. When a tiny bubble breaks.. those DOCs fall back down, and have to attach to some other surface of another bubble. Even though that may sound bad, my theory is that it is still "removed" from the system and will indeed be removed.

Regardless... your skimmer is properly sized for your tank. If you were trying to get a "little" bit more, and your skimmer was set deep in your sump, and you had wetter skimmate than you wanted. A extension would give a tad more room. One would not be the end of the world. More than that though, your skimmer is just undersized. Sell it and get another one. I just saw an add for 3 of them and that is just silly.

But here is the big down side. If you are adding extensions to increase length ON TOP OF the same water level, sump depth... then you are HURTING perfomace big time. Anything above the water line adds back pressure, and tiny changes in water level back pressure has HUGE effects on how much air it will draw and you will decrease through put.

 

I must say that I kind of disagree with your post. Increasing dwell time does help make the skimmer more efficient. You are moving the same amount of water but giving it more time to collect those DOC's. Now, is this something I would bother with? Nope it's not but it should serve it's purpose. This is one of the biggest reasons people run recirc skimmers and those work just fine. To be honest, theres better things to spend the money on though.

 

In design yes... but at the end of the road, it is only so efficient. And it should have been made that way when it was built. And like I said, if your skimmer is removing all the DOCs already...increasing performance does not remove more. It does decrease time need to remove them.

But taking a body and cramming more through it, or even taking a given skimmer and turning it into a "recirc" skimmer, does not increase dwell time. Because again, at the end of the day, the given skimmer can only process so much water.

With any type of contactor process, time is most certainly a function. Heat transfer, reaction processes. Leaving two processes in contact longer increases exchange. But a recirc skimmer does not actually increase time in contact...it increases number of passes. Again, the pump can only do so much. 1000 gph is a 1000gph. 750 gph or raw water, and 250 gph of processed water, does not equal 1000 gph of raw processed water. And it may or may not mean more total DOCs removed from the 1000 gal of water. Does that make sense.

Dwell time does matter, but only to the guys building it. The end user should have a product already tuned properly.

 

Thanks for the insight. after reading these posts and those on another board, I will not be getting the extension. my skimmer is at proper height and it is performing well. sometimes I need to learn to leave well enough alone.

biggest deciding factor was that adding more neck so I could raise water level in skimmer would only defeat the superior cone deisgn.

 

I can speak from experience, I have a 3" extension on a SRO 5000INT and IMO has made the skimmer more stable. My biggest beefs with the SRO skimmers is the neck and return piping is too short. I have also added a T section I made out of PVC and these 2 mods have enabled me to run the skimmer in 9" of water depth with no issues.

I feel the back pressure on the pump is a non issue, it already produces a lot of air and IMO borderline too much

 

That makes a lot of sense. Well said. This turned into a good thread!

matt

 

Azjohnny... thanks for your input. I greatly appreciate it!

 

I have added a 2nd neck extension, here are a few pics

https://picasaweb.google.com/lh/photo/VWTIwyocpgJKXpEIK8D8GNMTjNZETYmyPJy0liipFm0?feat=directlink



https://picasaweb.google.com/lh/photo/w9JYrg8DrDi4iq_FC-LKo9MTjNZETYmyPJy0liipFm0?feat=directlink