One more weird plumbing question; distance of pump from sump

[Anonymous]

Hey everyone!

Ya know the pipe that goes between the sump and the external return pump? Is there any reason to not make it longer?

I have an under house sump. Currently the return pump is about 14 feet away from the tank on the side of a 6 foot sump. I think moving the pump to the other side of the sump will save me 6 feet of water the pump won't have to pump (anyone know if I am wrong about that?). Continuing that thought, I could also extend the pipe the connects the sump to the pump about 8 more feet and thats 8 more feet of water the pump doesn't have to pump. I figure that elbows in that line would be a bad idea, but would a straight run of about 8 feet between the sump and pump be a good idea or would it hurt the pump or not lower head pressure enough to be worth the effort?

Does that make sense?

TIA

:mrgreen:

 

[MI0706]

Basically, anytime you can make a shorter run of pipe, with fewer bends, etc. will only raise pump performance on the outlet.

For the pumps inlet, you have to consider something called NPSH (net positive suction head)... The higher the NPSH, the better your pump will work... And lowering it will have just the opposite effects... NPSH will be affected by piping runs, placement of pump in accordance with its water source, etc.

Basically, you have to weigh both the output side and the input side and find that happy medium between the two.

 

[dizzy]

I would think that increasing the size of the pipe that goes from the sump to the inlet of the pump would help to negate any decrease in NPSH that was caused by the longer run. Probably wouldn't hurt to use a larger than needed pipe size and just reduce it at the pump, down to the size of the pump inlet. What size pipe currently runs from the sump to the pump?
Mitch

 

[Anonymous]

If you want to mave the pump away it should not be a bige deal. Upsize the suction line one pipe size and keep the elbows to a minimum. If the run you are trying to remove is horizontal then it is probably not afecting the system that much anyway.

 

[Anonymous]

Moving the pump further away from the sump can lead to some problems, particularly since the wter level in your sump creates virtually no intake head/pressure. Moving the pump further away may increase resistance on the intake side sufficient to cause some cavitation of the pump. However, this will probably not be a problem if you have enough back-pressure on the output of the pump, which it sounds like you do. In any event, you may want to increase the diameter of the plumbing from your sump to the pump intake (if that is an option). This will help reduce the frictional losses on the intake side. Otherwise, you may end up having to dial back the output with a valve to find the right balance.

 

[Anonymous]

Thanks so far!

The pump is an ampmaster 3000 and the line leading to it now is 1.5 inches. I could make it bigger when I move it - how big do y'all think is big enough?

It would be strictly a horizontal run and the inlet for the pump would be 2-3 inches from the bottom on the sump which is filled to about 15 inches.

Also, just to be blunt, if I remove 6-12 feet of the 14 foot lateral run that exists now, will that lower head enough to make moving the pump worth it, or am I just snark chasing?

 

[Anonymous]

Is your goal to save money or get more flow?

Reducing head pressure will pump more water but cost more also.

I have my pump about 4 feet from the sump, and when I set it up I had the impression that it could be a problem so I used a wider diameter in that section. As it it, my pump is dialed back so much it hardly matters.

 

[Anonymous]

The goal is to get more flow with existing equipment, so I don't have to spend much money.

Dan, what size is the inlet on your pump and what size pipe did you use for that 4 foot run? And, do you mean that with less head the pump will use more juice?

 

[Anonymous]

If you want to mave the pump away it should not be a bige deal. Upsize the suction line one pipe size and keep the elbows to a minimum. If the run you are trying to remove is horizontal then it is probably not afecting the system that much anyway.

Hmm. Actually, the run goes from the pump up three feet then over 14 feet, then up 5 or 6 more feet. It seems that since it goes up right away the horizontal run may be putting more pressure on the pump, but I don't know. :mrgreen:

 

[Anonymous]

Dan, what size is the inlet on your pump and what size pipe did you use for that 4 foot run?

If I recall correctly it's a 1.5 inch pump and I upped it to at least 2 inches.

And, do you mean that with less head the pump will use more juice?

Yeah, it spins faster. Seems odd, but true.

 

[Anonymous]

If you want to mave the pump away it should not be a bige deal. Upsize the suction line one pipe size and keep the elbows to a minimum. If the run you are trying to remove is horizontal then it is probably not afecting the system that much anyway.

Hmm. Actually, the run goes from the pump up three feet then over 14 feet, then up 5 or 6 more feet. It seems that since it goes up right away the horizontal run may be putting more pressure on the pump, but I don't know. :mrgreen:

The losses in a horizontal run are the friction losses. In a vertical run you get friction plus lift. So if you are looking to move the pump to reduce the friction losses you just going to be moving them to the suction side. If you increase the suction pipe diameter you can minimize the losses but some will still be there.

 

[Anonymous]

Dan, what size is the inlet on your pump and what size pipe did you use for that 4 foot run?

If I recall correctly it's a 1.5 inch pump and I upped it to at least 2 inches.

And, do you mean that with less head the pump will use more juice?

Yeah, it spins faster. Seems odd, but true.

Not excatelly true. The energy needed to run the pump is a function of several things. Alot depends on the impeller type. The motor will spin at roughly the same speed over the entire operation range of the pump and the difference will not be enough to mater. The equation is

Hp=(flow*head*S.G.)/(3960*pump eff)

Flow in gallons per minute
head in feet
S.G. specific gravity
3960 is a conversion to make the units work
pump eff is the pump efficiency (in most cases it varies over the performance cure and small pump are not known to be real efficient so around 80-85% would be a good range)

 

[Anonymous]

If you want to mave the pump away it should not be a bige deal. Upsize the suction line one pipe size and keep the elbows to a minimum. If the run you are trying to remove is horizontal then it is probably not afecting the system that much anyway.

Hmm. Actually, the run goes from the pump up three feet then over 14 feet, then up 5 or 6 more feet. It seems that since it goes up right away the horizontal run may be putting more pressure on the pump, but I don't know. :mrgreen:

The losses in a horizontal run are the friction losses. In a vertical run you get friction plus lift. So if you are looking to move the pump to reduce the friction losses you just going to be moving them to the suction side. If you increase the suction pipe diameter you can minimize the losses but some will still be there.

Great!
If I remove 8 feet of the horizontal run will I be removing enough friction loss to make any kind of significant difference, or am I just fooling myself and should start saving for a new pump?

 

[Anonymous]

Without knowing the details of you system I would guess that the flow increase would be minimal by moving the pump.

 

[Anonymous]

Righty, you may be better off changing your plumbing from 1.5" to 2" from pump output back to your tank. This will reduce the velocity, and consequently the frictional loss, of the water moving through the plumbing. This will probably have a much greater impact then moving the pump further away from the sump, particularly since, as someone pointed out, the total length of the run from the sump to the tank will not change and therefore where you stick the pump should not make any real difference. But note, your sump needs to be big enough to handle the extra volume of water inside your plumbing if and when your pumps shuts down.

 

[Anonymous]

Just to add to what GoM said. The frictional losses are a function of the velosity squared. I agree that the best bang for the buck would be to up size the piping back to the tank.

 

[Anonymous]

Not excatelly true. The energy needed to run the pump is a function of several things. Alot depends on the impeller type. The motor will spin at roughly the same speed over the entire operation range of the pump and the difference will not be enough to mater. The equation is

Well I'm no expert. When my tank was delivered short one drain hole, I called Sequence to see if it would be more economical to purchase a smaller pump since mine had to be restrained so much. They said that the difference was considerable, and with the pump dialed back it would be using no more power than their smallest pump going full bore.

 

[Anonymous]

If I move the pump to the other side of the sump I save about 6 feet, and if I connect it with 2 or 3 inch pipe, I can save another 4. Thats 10 feet of horizontal run that gets removed.
If I am understanding correctly, removing that much horizontal run will have minimal impact - though part of me wants to insist that removing 10 feet of pipe has got to make a difference.


I think I understand what you are saying about the larger pipe to the out, but due to current plumbing, I think it would be a major pain.

:mrgreen:

 

[Anonymous]

Just to add to what GoM said. The frictional losses are a function of the velosity squared. I agree that the best bang for the buck would be to up size the piping back to the tank.

Any idea how much bang we are talking about?

 

[Anonymous]

If I move the pump to the other side of the sump I save about 6 feet, and if I connect it with 2 or 3 inch pipe, I can save another 4. Thats 10 feet of horizontal run that gets removed.
If I am understanding correctly, removing that much horizontal run will have minimal impact - though part of me wants to insist that removing 10 feet of pipe has got to make a difference.


I think I understand what you are saying about the larger pipe to the out, but due to current plumbing, I think it would be a major pain.

:mrgreen:

I think we have some confusion. If the net distance from the sump back to the tank remains unchanged because you just moved the pump 6' further away from the sump and 6' closer to the tank, then you are correct that you will not reduce the overall frictional loss of the water traveling through the return plumbing. This would be a waste of effort.

IF. however, you are able to eliminate 6' of the total return run because you, for example, can move the sump closer to the tank or are now hooking up the plumbing to a side of the sump that is closer to the tank, then yes, you will have a net reduction in frictional losses.