Any concerns when throttling back return pump?

[SouthFla]

I'm really having a tough choice (as many must be for all the "what pump should I get" posts lol) determining my return pump for my 180G. My narrowed-down lists are (for the moment hehe) IwakiMD70RLT, GRI520, and Sequence2900SEQ21. The pump is returning from sump under stand to tank; tunze streams are used for supplemental flow.

My dilemas and resulting indecisiveness are a result of (1) the Iwaki's loud and energy hog (2) GRI loud, not as powerful (3) Sequence better energy and noise but too powerful (this is the smallest pump they currently make).

If I went with the Seq21, and because I only want 1200-1500gph going through my sump/refugium, is it bad to throttle the Sequence back from 2500gph to 1500 gph? Does this have any deleterious effects on the pump? The gate valve would of course be on the discharge side of pump...

Continued thanks for your input!

ja

[Jamesurq]

That's a pretty significant throttle back. I would think it would have an appreciable pernicious effect. Is it a pressure rated pump?

[kozmo02]

if you buy a pump that is too strong and throttle it back that much i would think it is probably pretty hard on the pump over time, i think you would be better off finding a smaller pump that works for you, maybe an AmpMaster.

[DMK]

southfla i have an iwaki 30RXT(1000GPH) which i have throttled down to around 700GPH. it's ok to throttle as long as u don't throttle 50% or more. i've also heard before that iwaki's are loud. all i know is mine is SILENT. it's not even bolted down either. i only have 1 complaint- it runs hot to the touch. i think once u go over the 30 and up to the bigger one's there may be a fan built in, just what i heard. all i can say is i'm happy w/ my choice and am a supporter of iwaki's. my main goal when buying a pump was dependability.

[Wazzel]

Most industrial pump manufactures reccomend not going below 25% of the rated flow of the pump. For aquarium use I would say this is a good run of thumb. If you do buy a larger than necessary pump and throttle it way down you will be waisting a lot of energy. It would be better to buy a smaller pump in your case somthing like a mag 18 would probably do the trick.

[mountainbiker619]

I recommend a Sen 900

[keodog]

Have you considered a Velocity T4. They run totally silent but do add a little heat to the water.

[jersey]

Have you thought about two smaller pumps? If heats not an issue a pair of velocity T-3's should do the job.

[cvye]

I'm running a GRI520 for return from a basement. Not totally silent, but not too bad, and very energy efficient.
I run a Blueline 55MD (Iwaki clone) for my skimmer, and that thing is very silent. I'm sure the 70MD version would be likewise.

[nematode]

Whether or not you can throttle back a pump or not depends on the pump. Read the manufacturer info. For example, the Dolphin Ampmasters can be throttled back and consume less energy when throttled back. Its a pretty quiet and efficient pump, but there have been some seal problems. I've had mine for a while and after getting over the fact that there would be a tiny little bit of leak from the seal I'ce come to really appreciate the pump.

[3twenty5]

I have throttled back a Mag and have found out it willusually snap the impeller shaft after awhile of backpressure

[Jamesurq]

what would be the difference to a pump between back pressure caused by increased head, and throttle back caused by a turned valve?

[vester_72]

That is a good question - I am not sure on that one.

I run an Iwaki 30rlt and have it throttled back about 30% and it seems perfect - plus very quiet.

If I have it at 100% it is LOUD. Plus, I do not want too much flow through my fuge, which is in my sump.

[Wazzel]

Originally posted by Jamesurq
what would be the difference to a pump between back pressure caused by increased head, and throttle back caused by a turned valve?

To the pump - nothing. Back pressure is back pressure weather caused by a valve or pluming.

[Wilafur]

create a bleed line from the return line back to the sump. this way you won't exert too much backpressure on the pump.

[SouthFla]

Boy, you guys are quick...Think you can also help me pick a contractor for my home addition :D

Great thoughts all, thanks! So many choices. But I think you answered my question and from your comments I feel that throttling back that much is not good. While bleeding off into the sump is a great idea, seems to me to be a waste of flow and energy. Perhaps I should just learn to live w/the Iwaki or GRI noise (or turn up the stereo hehe)...

[Wilafur]

i don't see how a bleed line will be a waste of flow or energy. consider the bleed line a "tap" line that you can use later down the road to provide flow into a chiller, skimmer, fuge, etc.

[Jamesurq]

you could always just get the big pump and double up on overflows.... Using all 4 holes to drain instead of just the 2. Use seaswirls on the 2 returns and you're done.

I'd love to only have 1 pump doing it all.

[CJ31]

I think some pumps can be throttled back w/out problem. I have an AM3k that is only pumping around 1200gph. Tom Jr at Dolphin said that pump can be throttled back 90% with no problem. However with the seal problems they have had, not sure I would recommend it though.

[mirski57]

Don't know if you made your decision yet...but I have a 180 tank..I tried the Iwaki 100 with a calculated 15' of head and it was WAAAYY too much. Then I tried an Iwaki 70 in my basement with the 15 foot head and still WAAYYY too much.(Still had to throttle it back at least 50%). This wekeend, I will try an Iwaki 55 and see how that goes.

My point is...If you are only putting this under your stand and have only 4 foot of head, an Iwaki 70 may be too much for the system.

Just my thoughts.

Mirski57