large pump intake and small bulkead

TekCat · 10/23/2006, 04:01 PM

I have drilled 3/4" hole in my tank for water intake on closed loop. Tank is filled with water and there is no way to redrill it.

(I know that if intake of the pump is too small then there is possibility of cavitation and other undesirable things.) So, would this work: intake manifold = 1' reduced to 3/4" bulkhead, then back to 1" pipe to powerfull pump that requires 1" intake?

BruiseAndy · 10/23/2006, 06:00 PM

You'll actually be more likely to cavitate the pump if you do that. No good solutions I can think of except for upsizing the hole or downsizing the pump.

TekCat · 10/23/2006, 11:51 PM

pardon my ignorance on plumbing and fliud mechanics... but wont it just increase water speed in the 3/4" part of the system? Or am I on drugs... again?

BeanAnimal · 10/23/2006, 11:59 PM

You can downsize the output section. This well lessen the overall throughput of the pump. This will not damage the pump... but you will get less flow.

The velocity of the water will increase as the pipe diameter decreases. But the pump IS NOT a positive displacement pump. Therefore as the pipe diameter decreases, the friction will increase (remember the velocity is rising). The pump will slip more trying to pull the water through the restriction.

Bean

BeanAnimal · 10/24/2006, 12:01 AM

Don't listen to HVAC tech guys... they are not the sharpest crayons in the pack...

In any case the HVAC guys is correct... your best bet is to upsize the hole or downsize the pump

Keelay · 10/24/2006, 12:59 AM

Here's my take. You can get around this easy with minimal risk of cavitating. Use Schedule 26 (thin wall) 3/4" PVC pipe.

1" Schedule 40 PVC has an inner diameter of 1.033 inches according to my favorite PVC diameter web reference:
http://www.gizmology.net/pipe.htm

1" Schedule 80 PVC is listed 0.935" I.D.

3/4" Schedule 26 PVC has an inner diameter of 0.9375". (Not listed on the site, but I took my own measurement with my own tape measure at 15/16")

That is 9% smaller than Schedule 40 and almost identical to Sched 80. I don't think it's going to matter much, if at all. I would bet money on it not cavitating ever.

3/4" sched 26 PVC

1" sched 40 PVC

Both pipes together.

- Kyle

BeanAnimal · 10/24/2006, 01:08 AM

I use thinwall on everything...substantially more area

Keelay · 10/24/2006, 02:00 AM

Yeah. I agree with you Bean. The more area the better. In an aquarium we're never concerned with pressure, and the thin wall pipe handles way more than we'll even need. There's really not much reason not to use the stuff.

I guess the question really is this when the pump has a 1" input, which Schedule I.D. is it referring to? I'm don't think I'm taking a leap here and thinking that the standard Sched 40 should work. The 3/4" thin wall is close enough to this that I believe there wouldn't be an issue.

I guess this is the time to ask TekCat what pump he's asking about.

RichConley · 10/24/2006, 08:31 AM

If the pump has 1" intake, it most likely needs 1.5"+ for a closed loop application.

You're either going to have to restrict the output, or run a smaller pump.

A smaller pressure rated pump with an eductor may be an option.

TekCat · 10/24/2006, 10:02 AM

I guess this is the time to ask TekCat what pump he's asking about.

Currently I have 3/4" intake -> Eheim 1262 -> OM-Squid -> four 3/4" outlets. I am quite dissapointed - not enough flow. So, I am thinking about upgrading pump to Pan World 50PX-X, however my dillema is 3/4" intake bulkhead, and the abovementioned pump has both 1" inlet and outlet.

96p993 · 10/24/2006, 10:17 AM

I certainly dont want to hijack this thread but along the same lines I have a output question for a closed loop. I have 4 outlets all of the 1" in diameter. I want to be able to direct the flow a bit but without 1" locline Im not how to do this.

BruiseAndy · 10/24/2006, 05:07 PM

Lots of reading for anyone who wants to take the time. This includes you bean (I assume you know how to read as you are posting here).

http://www.gouldspumps.com/cat_pf_0001.html

BeanAnimal · 10/24/2006, 05:25 PM

Don't be stealing my secret links and passing them out to the world!

I have several more pump theory and operation websites bookmarked of anybody is interested. I used to spend a LOT of time working with a LOT of different types of pumps (parent company I worked for did nothing but pumps!)

Bean

TekCat · 10/25/2006, 12:59 AM

Wow!!! that is a bit more than I bargain for

)))) I'd have to reread and reread that secret link.

Bean, could you explain for me in lamens terms what is positive displacement pump and what is NOT? I believe we're dealing with NON positive d.pumps.

BeanAnimal · 10/25/2006, 07:48 AM

Yes centrifugal pumps are not positive displacement.

On the other hand a PISTON pump is positive displacement. Spur gear pumps are positive displacement, etc.

What does this mean? A postive displacement pump is capable of moving the same amount of material with each cycle or stroke. As head pressure rises, the pump may slow down, but the material per cycle stays the same.

Does that help?

TekCat · 10/25/2006, 10:06 AM

Thanks Bean, makes perfect sense.

10/23/2006, 04:01 PM	#1
TekCat Registered Member Join Date: Sep 2005 Location: MN Posts: 3,130	large pump intake and small bulkead I have drilled 3/4" hole in my tank for water intake on closed loop. Tank is filled with water and there is no way to redrill it. (I know that if intake of the pump is too small then there is possibility of cavitation and other undesirable things.) So, would this work: intake manifold = 1' reduced to 3/4" bulkhead, then back to 1" pipe to powerfull pump that requires 1" intake?

10/23/2006, 06:00 PM	#2
BruiseAndy Registered Member Join Date: Jan 2003 Location: Ogden ut Posts: 896	You'll actually be more likely to cavitate the pump if you do that. No good solutions I can think of except for upsizing the hole or downsizing the pump. __________________ "Those who would give up essential liberty, to purchase a little temporary safety, deserve neither liberty nor safety." Current Tank Info: 150g and 75g

10/24/2006, 12:59 AM	#6
Keelay Registered Member Join Date: Oct 2006 Location: Gilbert, AZ Posts: 783	Here's my take. You can get around this easy with minimal risk of cavitating. Use Schedule 26 (thin wall) 3/4" PVC pipe. 1" Schedule 40 PVC has an inner diameter of 1.033 inches according to my favorite PVC diameter web reference: http://www.gizmology.net/pipe.htm 1" Schedule 80 PVC is listed 0.935" I.D. 3/4" Schedule 26 PVC has an inner diameter of 0.9375". (Not listed on the site, but I took my own measurement with my own tape measure at 15/16") That is 9% smaller than Schedule 40 and almost identical to Sched 80. I don't think it's going to matter much, if at all. I would bet money on it not cavitating ever. 3/4" sched 26 PVC 1" sched 40 PVC Both pipes together. - Kyle __________________ MobiLinc, a new way to experience your home. Visit the MobiLinc Store for low prices and the best quality on INSTEON home automation gear. Current Tank Info: 100G Custom Acrylic, 40 Gallon Sump, DIY Gravity Assisted Protien Skimmer, ATO, 2x175W MH + 1x96W VHO Actinic Last edited by Keelay; 10/24/2006 at 01:21 AM.

10/24/2006, 02:00 AM	#8
Keelay Registered Member Join Date: Oct 2006 Location: Gilbert, AZ Posts: 783	Yeah. I agree with you Bean. The more area the better. In an aquarium we're never concerned with pressure, and the thin wall pipe handles way more than we'll even need. There's really not much reason not to use the stuff. I guess the question really is this when the pump has a 1" input, which Schedule I.D. is it referring to? I'm don't think I'm taking a leap here and thinking that the standard Sched 40 should work. The 3/4" thin wall is close enough to this that I believe there wouldn't be an issue. I guess this is the time to ask TekCat what pump he's asking about. __________________ MobiLinc, a new way to experience your home. Visit the MobiLinc Store for low prices and the best quality on INSTEON home automation gear. Current Tank Info: 100G Custom Acrylic, 40 Gallon Sump, DIY Gravity Assisted Protien Skimmer, ATO, 2x175W MH + 1x96W VHO Actinic

10/24/2006, 08:31 AM	#9
RichConley Registered Member Join Date: Sep 2004 Location: Bostonian in Chicago going to DC Posts: 9,908	If the pump has 1" intake, it most likely needs 1.5"+ for a closed loop application. You're either going to have to restrict the output, or run a smaller pump. A smaller pressure rated pump with an eductor may be an option. __________________ NO TANKS!!!

10/23/2006, 11:51 PM	#3
TekCat Registered Member Join Date: Sep 2005 Location: MN Posts: 3,130	pardon my ignorance on plumbing and fliud mechanics... but wont it just increase water speed in the 3/4" part of the system? Or am I on drugs... again?

10/23/2006, 11:59 PM	#4
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	You can downsize the output section. This well lessen the overall throughput of the pump. This will not damage the pump... but you will get less flow. The velocity of the water will increase as the pipe diameter decreases. But the pump IS NOT a positive displacement pump. Therefore as the pipe diameter decreases, the friction will increase (remember the velocity is rising). The pump will slip more trying to pull the water through the restriction. Bean

10/24/2006, 12:01 AM	#5
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	Don't listen to HVAC tech guys... they are not the sharpest crayons in the pack... In any case the HVAC guys is correct... your best bet is to upsize the hole or downsize the pump

10/24/2006, 01:08 AM	#7
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	I use thinwall on everything...substantially more area

10/24/2006, 10:02 AM	#10
TekCat Registered Member Join Date: Sep 2005 Location: MN Posts: 3,130	I guess this is the time to ask TekCat what pump he's asking about. Currently I have 3/4" intake -> Eheim 1262 -> OM-Squid -> four 3/4" outlets. I am quite dissapointed - not enough flow. So, I am thinking about upgrading pump to Pan World 50PX-X, however my dillema is 3/4" intake bulkhead, and the abovementioned pump has both 1" inlet and outlet.

10/24/2006, 10:17 AM	#11
96p993 Registered Member Join Date: Oct 2004 Location: Mckinney, Tx Posts: 1,130	I certainly dont want to hijack this thread but along the same lines I have a output question for a closed loop. I have 4 outlets all of the 1" in diameter. I want to be able to direct the flow a bit but without 1" locline Im not how to do this.

10/24/2006, 05:07 PM	#12
BruiseAndy Registered Member Join Date: Jan 2003 Location: Ogden ut Posts: 896	Lots of reading for anyone who wants to take the time. This includes you bean (I assume you know how to read as you are posting here). http://www.gouldspumps.com/cat_pf_0001.html __________________ "Those who would give up essential liberty, to purchase a little temporary safety, deserve neither liberty nor safety." Current Tank Info: 150g and 75g

10/24/2006, 05:25 PM	#13
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	Don't be stealing my secret links and passing them out to the world! I have several more pump theory and operation websites bookmarked of anybody is interested. I used to spend a LOT of time working with a LOT of different types of pumps (parent company I worked for did nothing but pumps!) Bean

10/25/2006, 12:59 AM	#14
TekCat Registered Member Join Date: Sep 2005 Location: MN Posts: 3,130	Wow!!! that is a bit more than I bargain for )))) I'd have to reread and reread that secret link. Bean, could you explain for me in lamens terms what is positive displacement pump and what is NOT? I believe we're dealing with NON positive d.pumps.

10/25/2006, 07:48 AM	#15
BeanAnimal Registered Member Join Date: Feb 2003 Location: Pittsburgh Posts: 20,772	Yes centrifugal pumps are not positive displacement. On the other hand a PISTON pump is positive displacement. Spur gear pumps are positive displacement, etc. What does this mean? A postive displacement pump is capable of moving the same amount of material with each cycle or stroke. As head pressure rises, the pump may slow down, but the material per cycle stays the same. Does that help?

10/25/2006, 10:06 AM	#16
TekCat Registered Member Join Date: Sep 2005 Location: MN Posts: 3,130	Thanks Bean, makes perfect sense.