Two pumps for more flow?

Caffinehog · Jul 7, 2003

Has anyone in here used a second pump for more flow? I know that you lose a lot of pump power from back pressure from the system. So why not just use a second pump to double the pumping power? You could put it anywhere in the system.

Joker_927 · Jul 7, 2003

I would like to know this answer. Would 2 x 175 GPH = 1 350 GPH pump?

thorilan · Jul 7, 2003

I would like to know this answer. Would 2 x 175 GPH = 1 350 GPH pump?

please dont take this wrong as i illistrate..

does 2 ford escorts both teathered to a 20 ton trailler double the speed?

they increase the power but they do not double it but in some places the speed will be faster because it will have more force but nowhere near double

i could be wrong but this is pretty much what i have seen

Mustanley · Jul 7, 2003

Running two identical pumps in parallel will increase your flow rate, while running two pumps in series will increase pressure and head capacity of your system.

AreUCrzy · Jul 7, 2003

Mustanley said:
Running two identical pumps in parallel will increase your flow rate, while running two pumps in series will increase pressure and head capacity of your system.

what you mean by in parallel??

Mustanley · Jul 7, 2003

Parallel (use wye adapters to split and recombine water lines)
>------Pump--------->
>------Pump--------->

Serial
------->Pump---->Pump----->

aka665 · Jul 7, 2003

that reminds of Electricity

1/R+1/R=1/R(eq)........

Caffinehog · Jul 7, 2003

Yeah... pressure is a biggie in watercooling. A watercooling system causes so much back pressure that a 250gph pump may be only pumping 30gph.

Mustanley · Jul 7, 2003

I've been thinking about adding a second danner mag3 pump in serial. In my application, the water is pumped vertically almost 4' in the air. Once I add the restriction of a cpu and gpu block, I may need that extra pressure.

thorilan · Jul 7, 2003

Running two identical pumps in parallel will increase your flow rate, while running two pumps in series will increase pressure and head capacity of your system.

this is what i was trying to say but yesterday wasnt a good day (couldnt seem to get anything right)

Paxmax · Jul 8, 2003

I won't matter much if you put them in parallell or series. The flowrate will in both cases increase through a system.

It will increase because both pumps now work on a different place on the P/Q curve. I.E. lift height /against/ volume output.
A pump can pump more water if the resistance or lift height is lower. Once you increase the resistance the waterflow will decrease and mag-drive pumps aren't linear devices.

bigben2k · Jul 8, 2003

Mustanley said:
I've been thinking about adding a second danner mag3 pump in serial. In my application, the water is pumped vertically almost 4' in the air. Once I add the restriction of a cpu and gpu block, I may need that extra pressure.

If it's in a loop, it's not relevant: you have 4' feet up, and 4 feet down, and they'll cancel each other out.

What you do have though, is added flow restriction from the tubing.

thorilan · Jul 8, 2003

the added head pressure more than makes up for what little extra tubing is added

Mustanley · Jul 8, 2003

bigben2k said:
If it's in a loop, it's not relevant: you have 4' feet up, and 4 feet down, and they'll cancel each other out.

What you do have though, is added flow restriction from the tubing.

It's not in a loop. I'm using an open evaporative system. Regardless, while two pumps in serial will not give you greater theoretical flow, it will help you to better overcome restrictions in the system, i.e. waterblocks, radiators, tubing bends, etc. So in reality, the more restrictive the system, the more benefit two pumps will give you. I'm not following your logic here.

Owenator · Jul 8, 2003

Paxmax said:
I won't matter much if you put them in parallell or series. The flowrate will in both cases increase through a system.

It will increase because both pumps now work on a different place on the P/Q curve. I.E. lift height /against/ volume output.
A pump can pump more water if the resistance or lift height is lower. Once you increase the resistance the waterflow will decrease and mag-drive pumps aren't linear devices.

Actually in the case of serial the flowrate will probably not increase as much as parallel. Parallel flow allows the two pumps to "share" the job of overcomming the flow resistance. Two pumps also double the fluid volume moved. The only problem is that at higher flowrates resistance inthe lines heatercore water block et al increase.

Two pumps in the same line is often called "multi-stage", infact sime pumps are made this way on purpose to get higher pressures. Two serial pumps (in the same line) increase pressure which can over come the resitance better but you will not get double the flowrate.

It really comes down to what you need. More flowrate of higher pressure/head capability. As one person said if you want to pump the water higher two pumps in series is you setup. If you want higher flowrates you would want parallel pumps. Once caveat with series pumps is that the flowrate would be equal to the flowrate of the slowest of the two pumps so match them well.

O

Mustanley · Jul 8, 2003

Owenator said:
Actually in the case of serial the flowrate will probably not increase as much as parallel. Parallel flow allows the two pumps to "share" the job of overcomming the flow resistance. Two pumps also double the fluid volume moved. The only problem is that at higher flowrates resistance inthe lines heatercore water block et al increase.

Two pumps in the same line is often called "multi-stage", infact sime pumps are made this way on purpose to get higher pressures. Two serial pumps (in the same line) increase pressure which can over come the resitance better but you will not get double the flowrate.

It really comes down to what you need. More flowrate of higher pressure/head capability. As one person said if you want to pump the water higher two pumps in series is you setup. If you want higher flowrates you would want parallel pumps. Once caveat with series pumps is that the flowrate would be equal to the flowrate of the slowest of the two pumps so match them well.

O

Good explanation, I concur. :thup:

Owenator · Jul 8, 2003

Mustanley said:
Good explanation, I concur.

Thanks!

I've been thinking about this also lately because I am toying with making an external water cooling "box" like Corsair and migrating my system to a tooless case with the hoses coming in from the back.

rogerdugans · Jul 8, 2003

Just a note:
Head (in relation to water cooling pumps)

Static head- the height a pump will get a liquid to in a free standing tube

Friction Head- the resistance added by all components in the system: blocks, radiators, reservoirs and T-Lines, fittings, and tubing.

Pumps are usually rated by Static Head but the type that impacts us most (with in-case systems; external systems often have more static head) is Friction head.
Longer tubing and tight radius bends or fittings can make a big difference.

Caffinehog · Jul 8, 2003

Static head is nonexistent in all but bong systems. Everywhere else, the siphon effect, the water being pulled down by gravity on the other side of the system, cancels it out. Friction is the enemy.

Owenator · Jul 8, 2003

Caffinehog said:
Static head is nonexistent in all but bong systems. Everywhere else, the siphon effect, the water being pulled down by gravity on the other side of the system, cancels it out. Friction is the enemy.

It is general practice to cancel out graivty head on closed loop pump system. But, static head does exist when the pump starts up but after it is running (assuming it can overcome the initial static head) they do cancel out. As a person said they have a system with a four foot height difference there is the possiblity that a weeker pump might not even be able to reach the highpoint in the system.

I am assuming you start with empty lines. If you could fill the lines fully you would then gain the 'syphon' effect you mentioned on the "down" side even at pump startup. This might be an issue if you had an empty system with a reservoir at the pump.

That said, rating a pump at static head is just an easy way to describe the maximim pressure the pump can put out (in feet of water usuallly). Also of interest is that most pumps list their output at 1 foot of static head not zero but that is more "marketing". My pondmaster 250 for example will put out 250GPM at 1 foot of head and 275GPM with no resistance. It's maxium head is stated as 7ft.

O

Two pumps for more flow?

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