Iwaki pressure question

god910 · #1 01/23/2007, 12:32 AM

Okay, I've got an Iwaki WMD-30RLXT, and it's rated at 960 gph at 4 ft. It's rated at a max head of 13.5 ft.

My question is this (this makes total sense to me, just makes sure my thoughts aren't skewed) If I use a ball valve to limit flow, it'll obviously increase pressure. But would it not increse pressure in the same way that a head increase would?

I just don't want to hurt the pump. My overflow isn't capable of keeping up with this pump, and I'd really like the increased flow. I'm currently running a horribly crappy pump, and I'm getting ready to construct a new sump/ref. and I'd like to go ahead and drill it for this pump. Any input would be appreciated.

joelamb7467 · #2 01/23/2007, 01:19 AM

If you are planning on restricting it at all you should go for the RLT, not the RLXT. The RLXT is not supposed to have any restriction. I suppose you could simulate the head pressure with a ball valve, but you wont really know how much pressure you are putting on the pump. Better safe than sorry.

god910 · #3 01/23/2007, 01:29 AM

Thanks so much. I didn't know this about the RLXT. I haven't been able to find out much info on this pump, and I got it used. I traded it for some automotive work.

jdieck · #4 01/23/2007, 02:04 AM

Here is the performance chart comparing the Z, the RT and X
Yours is the purple line.
From it you can restrict it without problem to 10 ft head (about 600 gph)
http://iwakiwalchem.com/nav/CMImage....e=30FAMcrv.pdf

god910 · #5 01/25/2007, 11:09 AM

Thanks alot for that graph. I see you're in Naperville. I'll be in your neck of the woods in March. Sure wouldn't mind seeing that 225 *wink wink*

RichConley · #6 01/25/2007, 01:08 PM

Quote:

Originally posted by god910

My question is this (this makes total sense to me, just makes sure my thoughts aren't skewed) If I use a ball valve to limit flow, it'll obviously increase pressure. But would it not increse pressure in the same way that a head increase would?

Yes, the pump sees a partially closed ball valve exactly the same as it sees increased head.

the other tang · #7 01/25/2007, 01:44 PM

Rich is right, no difference. However as written above you don't know how much you are restricting the flow and how much back pressure you are creating. Two things come to mind. First beaker the flow, get a 1g or 5g container and a stopwatch. If it takes ( simplest of terms)10min to get 10g then gph would be that X 6.

The second is a best of both worlds solution providing you sump allows for it, simply t off and re direct the flow right back into the sump. Use a ball valve to get the flow where you want it in the display and let the rest dump through the loop back to the sump.

RichConley · #8 01/25/2007, 03:02 PM

Quote:

Originally posted by the other tang

The second is a best of both worlds solution providing you sump allows for it, simply t off and re direct the flow right back into the sump. Use a ball valve to get the flow where you want it in the display and let the rest dump through the loop back to the sump.

Thats not the Best. Your pump will run hotter that way, use more energy, and most likely die sooner.

jdieck · #9 01/25/2007, 06:24 PM

Quote:

Originally posted by god910
Thanks alot for that graph. I see you're in Naperville. I'll be in your neck of the woods in March. Sure wouldn't mind seeing that 225 *wink wink*

Welcome any time

jmuscat2 · #10 01/25/2007, 10:15 PM

Quote:

Thats not the Best. Your pump will run hotter that way, use more energy, and most likely die sooner.

Why would allowing some of the flow to go back to the sump through a tee cause the pump to run hotter and die sooner? You are correct though that it will use more energy.

If you close the ball valve on the discharge of the pump it will increase the head pressure on the pump which reduces the flow. The amount of energy used is also reduced. You can throttle the pump with a ball valve within reason without doing any damage. Ideally you would want to shave the impellor to reduce the flow, but this is not easily reversible should you need more flow at a later date.

jdieck · #11 01/26/2007, 12:34 AM

jmuscat2:

The power consumption of the pump increases with the flow while the efficiency increases with the flow and then starts to decrease again past certain flow level usually between 50 to 75% of the flow capacity were the higher efficiency lay.
At a restricted flow the pump will be using less power so the motor will be doing less work although potentially at lower efficiency which translates in a bit more of power wasted on heat. Despite this the amount wasted on heat is less than the heat generated by working at full capacity.
Now this is regarding the efficiency of the pump.
Regarding the overall efficiency of the system, say if you need 50% capacity then returning the rest of the flow will give for the pump a 100% consumption for 100% of the flow which is more efficient but for the system will give 100 % consumption with 50% of the flow.
Restricted the consumption will be say 60% of the power for 50% of the flow which is less efficient for the pump but for the system you still get a 40% power reduction.
By the way, running restricted is less chance of cavitation and vibration than running at full flow capacity.

cherubfish pair · #12 01/26/2007, 12:56 AM

Quote:

Originally posted by jdieck
Here is the performance chart comparing the Z, the RT and X
Yours is the purple line.
From it you can restrict it without problem to 10 ft head (about 600 gph)
http://iwakiwalchem.com/nav/CMImage....e=30FAMcrv.pdf

Who sells the RZT iwakis? And are the Zs best for closed loops?

jdieck · #13 01/26/2007, 01:06 AM

Quote:

Originally posted by the cattleman
Who sells the RZT iwakis? And are the Zs best for closed loops?

No the Z is for high discharge pressure (lower flow) more suited say if your sump is in the basement and need to pump to the uper floor.
For a closed loop (very low head) the X is more suitable.

Any Iwaki distributor shall be able to supply the different models although they might not have them in inventory they shall be able to order it for you or you can contact Iwaki:
http://iwakiwalchem.com/nav/cm.aspx?NavID=103&CMID=21

cherubfish pair · #14 01/26/2007, 01:29 AM

So.. flow is volume per time right? And pressure is the strength of the pump to push water? What's head pressure?

jdieck · #15 01/26/2007, 03:05 AM

Quote:

Originally posted by the cattleman
So.. flow is volume per time right? And pressure is the strength of the pump to push water? What's head pressure?

Head pressure is also pressure but in different units of measure.
Say, one feet of head pressure is the pressure exerted by a column of water of one feet high which is equivalent to 0.4348 pounds per square inch. In other words 1 psi is equivalent to the pressure of the water at the bottom of a tank 2.3 feet high.

There is two effects that cause counter pressure at the discharge of a pump.
a) Hydrostatic pressure. This is the head pressure created by the colum of water. In other words how high the water has to be pumped from the surface of the water in the sump to the surface of the water in the aquarium. It is created by the weight of the water.

b) Dynamic pressure: This is created by the water velocity trough a pipe and fittings due to friction and changes in direction. The higher the flow the higher the velocity the higher the oposing pressure to the circulation of the water. The more fittings and the smaller the diameter of the pipe the higher the friction so the higher the oposing pressure to the circulation of the water

The sum of both pressures (a and b above) is what gives the total head pressure the pump needs to overcome

In simple terms a pump with a higher discharge head pressure can pump the water to a higher level or trough more fittings using a smaller pipe diameter.

In a closed look the hydrostatic pressure (a above) is zero as the difference in height from the water surface on the inlet to the water surface in the outlet is zero (same water level, the tank surface in both the inlet and the outlet. So in a closed loop the only head the pump needs to overcome is that created by the piping when the water is flowing.

the other tang · #16 01/26/2007, 10:05 AM

Well done Jdieck, we use different terms but the result is the same.

So.. flow is volume per time right?

Yes sir, a gallon jug will not tell you precisely but close enough for a tank.

Sorry I never consitered the power consumption, in my line of work it is an afterthought.

the other tang · #17 01/26/2007, 10:08 AM

jdieck, the higher sg of sw would change the head right? I know it won't be a ton off, but for the sake of knowing. I use the generic .5psi per ft to figure jobs, and has never failed me. Although your 0.4348 is correct, just easier to do the math in your head bases on .5 .

RichConley · #18 01/26/2007, 11:19 AM

IIRC, you should be able to just multiply that .4348 number by 1.025 to figure out what salt water would be, but like you said, the change is miniscule.

jdieck · #19 01/26/2007, 12:15 PM

Quote:

Originally posted by the other tang
jdieck, the higher sg of sw would change the head right? I know it won't be a ton off, but for the sake of knowing. I use the generic .5psi per ft to figure jobs, and has never failed me. Although your 0.4348 is correct, just easier to do the math in your head bases on .5 .

Yes, Pump head pressure assumes pure water, with sea water the actual height reached will be about 2.5% less but because most calculations of dynamic head pressure have a margin of error higher than that the 2.5% ( or the difference between the 0.5 and 0.4348) usually becomes unnoticeable.

cherubfish pair · #20 01/29/2007, 03:59 PM

So when a pump is rated at 460 gph @ 3', that's not @ 3' of head pressure?

jmuscat2 · #21 01/29/2007, 04:50 PM

Yes it as rated a 3' of head pressure. This includes the pressure from resistance in pipes as well as an head pressure needed to lift water a given height.

god910 · #22 01/29/2007, 06:17 PM

Holy smokes, this thread blew up, and I didn't even know. For some reason I just recieved my first email notification.

Anyhow, thanks alot for a great explanation of everything. I might have an easy enough fix for this whole situation. I've been getting mad at my basement lately. (it's messy) It's finished with complete bathroom/shower, and a kitchen. Well we haven't used it for any good in the 3 years we lived here, so I've decided (pump dependant) on moving my sump into the basement. I've been wanting to setup a pod cultivation tank, a larger tank just for growing more (and different kinds) of algae, and a better place to easier access my skimmer and setup the large x huge Ca reactor I've got. I'd already started planning the new sump I was gonna setup and I'm thinking I'll just set everything in the basement below the tank. So here's my *new* question.

This pump has a 1" oulet, I've seen people using oversized outlet lines (such as a 2" line on a 1" outlet, etc.) does this actually help? I've always figured that no matter how big the line was your limiting factor would be the smallest I/D in the whole system. I understand a 2" line would give you more flow with less pressure, I'm just trying to figure out the best way to set this up. Is this pump even a good candidate for that? I will be upgrading the system at a later date because I'm going to be setting up my 210 as a reef tank some time in the future, and know I'll need a much larger pump (It's gonna have alot more head pressure, because the tank is on a slab, and some major plumbing is gonna be involved.)

This will pretty much be straight up and back down. Not alot of trickery.

jdieck · #23 01/29/2007, 06:34 PM

As jmuscat2 mentions the 3' is not necessarily the actual height it will be lifted, you need to deduct the head pressure generated by the piping and fittings.
That pump usually can handle a higher head pressure (say 5 or 6 ft) but the flow rate drops accordingly. To know how much the flow will drop you need the pump's performance curve.
With the pump curves you shall be able to better compare pumps at your actual estimated head pressure.
As an example (See the charts below). An Iwaki 20 RT at 3 feet will give you a flow of around 425 gal/hr and a max flow of 480 gal per hr at 0 feet while a Mag 7 will give you 700 gal/hr at 0 ft and 525 gal per hr at 3 feet. So apparently the Mag 7 will be a larger pump but if you are operating the pump at 8 ft then the Mag drive will give you 260 gal/hr while the Iwaki will give you 280 gal/hr. Also although the Iwaki starts at a lower maximum flow it has a maximum head pressure (15 feet) than the Mag 7 (13 feet).
That can tell you a couple of things, first that the Iwaki will handle pressure a bit better (so it will be a better pump if you are using say a SCWD) than the Mag 7 and that although the power consumption per gal of flow of the Mag 7 will be better at lower head pressure the power consumption of the Iwaki will be better at higher head pressures.
Although there are other considerations like price, external vs internal, quality of manufacture and expected life etc. the information on the performance charts can be invaluable when selecting a pump.

jdieck · #24 01/29/2007, 06:46 PM

Quote:

Originally posted by god910

This pump has a 1" oulet, I've seen people using oversized outlet lines (such as a 2" line on a 1" outlet, etc.) does this actually help? I've always figured that no matter how big the line was your limiting factor would be the smallest I/D in the whole system. I understand a 2" line would give you more flow with less pressure, I'm just trying to figure out the best way to set this up. Is this pump even a good candidate for that?

No the limiting factor is not the smallest diameter specially not the discharge diameter of the pump connector.
the pump characteristics are set from the outlet out that means that if you want to reduce your head pressure (to increase the flow) you need to use larger diameter for the piping and reduce the number of fittings and valves. This is true even for tank bulkheads. It is a lot less head pressure from a pipe that is 1-1/2" dia with bulkheads of 3/4" than a pipe of 3/4" with the same 3/4" bulkheads. The longer the pipe and the higher the number of fittings the larger the diameter shall be for a cmparable head pressure.
As an example, Mag drives 9 and 12 have an outlet diameter of 3/4" but because the Pumps high rate of flow drop with increased head pressure the manufacturer recomends the use of 1-1/2 pipe diameter.
So in your case from the basement (high static head and longer runs) I would recommend using first a pump that can handle pressure better than flow, go with the highest practical pipe diameter (say 11/2") and avoid the use of elbows as much as possible by using flex PVC (which is not that flexible but smooth) for smoother curves and to limit valves to a max of one for maintenance purposes.

the other tang · #25 01/31/2007, 10:09 AM

JD is exactly right, we call it pressure drop here . Nonetheless same thing. In a simple example, the water volume you'd get from a water faucet would be greatly decreased if you connected a 50' hose. It would continue to decrease if you added another and another and so on. Although the static pressure would stay the same the volume would decrease. I am looking for my old pressure drop program to post here to make this easier for any who chose to use it. Quite simply, use big pipe and fittings and let the pump flow, use a valve to restrict if you need to. The flex is a great idea 90's are a flow killer, 2 45's have a much smaller impact on flow. Flex would have next to no impact.