How will reducer bushings affect pump?

[RobertK]

Hi,
I have 3/4" plumbing but I'm looking at a return pump with 1" inlet/outlet. It is not a pressure-rated pump. I'm wondering, if I use 3/4-1" bushings on both sides of the pump how will it affect things? Flow rate, pump wear, microbubbles, etc. Anyone know?
Thanks,
Robert

 

[BeanAnimal]

IT will reduce the output slightly due to backpressure and friction...

If it causes enough resistance on the intake side it may cause cavitations.

Could you provide more information?

1) pump model
2) plumbing details before and after the pump, including length and height, bulkhead details etc.

You will likely be fine, but given more information we can give you a better answer.

 

[Icefire]

reduced flow for sure

 

[RobertK]

Iwaki 20 RXLT

inlet side - 18" of 3/4" rigid pipe coming from sump w/ two 45 degree ells 4" in front of pump inlet

outlet side - 3/4" union --> 5' of 3/4" flexible PVC pipe covering a 4' rise --> another union --> 2 90 degree ells then locline tubing into tank

current pump = PanWorld 40PX - approximately the same flow rate, pressure-rated, 3/4" inlet/outlet

If the bushings are a problem I could get the 20 RLT, which is pressure rated (don't really need that for a return pump) and has 3/4" inlet/outlet, but I think I'd get a little more flow out of the RXLT

Thanks,
Robert

 

[BeanAnimal]

That little bit more flow will be reduced somewhat by the plumbing. I have never owned either pump so can not give you first hand impressions.

3/4 IS fairly small though. Myabe some 20RXLT users will chime in.

 

[rfequity]

Better not to restrict the intake side. Reducing the output is fine. This is true for all pumps. If you do you will shorten the life of the pump and possible cavetation.

 

[BeanAnimal]

BUT:

You can reduce the intake if you also reduce the output side accordingly. The net result will be more head on the pump and therefore less suction!

You can neck any pumps intake down as long as the output is restricted enough to prevent cavitation.

Cavitation damages pumps because of the violent buffeting of the impeller and the wear and stress tha it causes. Prevent the cavitation (choke down the output) and the pump will be as happy as ever (and even draw less power).

Bean

 

[RobertK]

I checked the RC Head Loss Calculator - not sure if it is accurate in this scenario but according to that there is indeed about a 1' increase in head pressure and about 80 GPH decrease in flow rate if running the 20 RLXT with 3/4" pipe on the outlet compared to the 1" pipe it is threaded for (400 vs. 480 GPH) on my setup. Bushed down to 3/4" that's only about 30 GPH more than the 20 RLT gives with its standard 3/4" threads (370 GPH), according to the calculator. The risk of cavitation with the RLXT may not be worth the small increase in flow over the RLT.

 

[BeanAnimal]

As I have not run either pump, I can not say if you will have a problem.

I would guess the RXLT draws less current, or are they the same motor?

 

[DarG]

Blueline is a relabeled Pan World. Blueline is supposed to be designed by an ex Iwaki engineer, which means he designed that line of Pan World pumps which are relabeled by Blueline, Coralife, and others. They have equivalent curves and are supposed to be slightly quieter than the Iwaki's. In other words, if the Pan World has the same flow curves as the Iwaki that you are thinking of replacing it with, the Iwaki will not be a stronger pump. I can tell you that those Pan World pumps do not inflate their specs, if anything they are a little conservative. I replaced a Little Giant with a Pan World that was rated for the about the same flow (actually a little less) as the LG, both pressure rated, and the Pan World was actually stronger.

 

[RobertK]

Bean,
I think it is the same motor. Same speed, same output in HP. The RT draws .48 amps and the RXT .50 according to Iwaki's website.

DarG,
Yes, the PanWorld 40 PX, aka Blueline 20 HD, is supposedly comparable to the Iwaki 20 RLT, but there is no PanWorld equivalent of the 20 RLXT, which is Iwaki's higher flow, non-pressure-rated version of the RLT. That's why I was wondering if I could get more flow with the RXLT than with the RLT/40PX, without adding more heat to the water.

Note that PanWorld makes a 50 PX and a 50 PX-X, aka Blueline 30 HD and 30 HD-X, which are comparable to Iwaki's 30 RLT and RLXT, respectively. All of the pressure-rated pumps mentioned have 3/4" fittings and the non-pressure rated versions have 1" threads.

Thanks,
Robert

 

[BeanAnimal]

Likey the only difference is the impeller and volut then

Ckoking the flow pump down to keep it from cavitation or using the pressure pump... who knows. I would bet they will both be right in the same ballpark with regards to flow and electrical consumption on your setup. You may even be better off with the flow model choked down (less power consumption).

The big difference is at much higher heads, where the flow model would be left in the dust.

 

[DarG]

<a href=showthread.php?s=&postid=10038853#post10038853 target=_blank>Originally posted</a> by RobertK
Bean,
I think it is the same motor. Same speed, same output in HP. The RT draws .48 amps and the RXT .50 according to Iwaki's website.

DarG,
Yes, the PanWorld 40 PX, aka Blueline 20 HD, is supposedly comparable to the Iwaki 20 RLT, but there is no PanWorld equivalent of the 20 RLXT, which is Iwaki's higher flow, non-pressure-rated version of the RLT. That's why I was wondering if I could get more flow with the RXLT than with the RLT/40PX, without adding more heat to the water.

Note that PanWorld makes a 50 PX and a 50 PX-X, aka Blueline 30 HD and 30 HD-X, which are comparable to Iwaki's 30 RLT and RLXT, respectively. All of the pressure-rated pumps mentioned have 3/4" fittings and the non-pressure rated versions have 1" threads.

Thanks,
Robert

Ok, I see what you are looking for. There is a Blueline 55HD which is equivalent in flow at 15 GPM but is pressure rated and has 1" input and output. It's also 180 watts. Not what you are looking for though. I have one. Good pump.

 

[RobertK]

Here are the pump curves. The curve labeled Standard is the 20 RLT and the one labeled High Flow is the 20 RLXT. It looks like they intersect at 6 feet of head pressure, i.e. below 6' the RLXT has higher flow and above 6' the RLT does.

According to the head loss calculator, I'd have 5.44 feet of head pressure with the RLXT bushed down to 3/4" (for about 465 GPH eyeballing the chart), and 5.25 feet of head pressure with the RLT (about 420 GPH), i.e. about 10% increased flow with the RLXT if it doesn't cavitate. Not sure its worth the risk and effort.

Thanks,
Robert

 

[sjm817]

I'm not wild about reducing plumbing sizes. I usually try to increase it. External pumps handle head a lot better than submersibles but... If it isn't a ton of trouble, I would redo the pluming setup.

 

[RobertK]

I'm not wild about redoing plumbing setups (yes, it would be a ton of trouble), but I'm beginning to think you may be right.

Thanks,
Robert