Return pump pressure head and friction loss

[Jackooze]

sup everyone , I am having difficulties understanding head pressure and friction loss. I recently moved my sump into the basement. My tank is a reefer 250 which uses 3/4” return plumbing and I am using Vectra M1 pump which has an outlet 3/4”. The sump return line goes up to ceiling 4ft across the basement ceiling 11ft and then up 4ft to the tank. Running the pump at 100% I get 180gph according to the apex flow meter. I figured the pump was not strong enough so I purchased the new Vectra L2 3100gph. The outlet fitting is 1.25 which I had to reduce to 3/4” to fit my existing plumbing. Now I set this pump to 100% as well and the water in the return pump chamber started rumbling but the gph did not exceed 168. The flow inside the display tank return nozzles were weak just like the old pump.

So here are my questions ?

Shouldn’t a 3100gph pump preform better then a 2000gph in flow ?

Is my head pressure that bad that either of these pumps can’t preform higher then 180gph ?

should I replace return line to 1” even if the tank has 3/4” return nozzles?

Reducing the Vectra L2 pump from 1.25 to 3/4” will that cause performance loss ?

 

[Potatohead]

Unfortunately the vectras don't do well against head pressure. The L2 will flow better, but you would need to upgrade the pipe from 3/4" to 1" or even 1.25".

The problem with just getting a beast of a pump and using the 3/4 is it will use a lot more power than necessary. Upgrading the line will be far cheaper in the long run.

However with all that said, if you are getting a real 180 gph, that is likely just fine for a 65g tank.

 

[DCR]

Your elevation gain alone is 15 feet of head. Adding the friction losses at probably 2-4 ft and you are all the way back on the curve of the L2 which maxes out at about 21 ft with zero flow. As the backpressure (head) on the discharge of a pump increases, the flow is reduced. The end of curve, zero head flow rate is meaningless - especially in your basement application. Vendors post these values but you rarely can get more than about 50% of the flow even in an ideal set-up.

You will need a much higher head pump. You did not say how much flow you would like to have, but the two 3/4" returns are practically going to limit you to about 600-900 gph total. I would increase the line size to 1" or even 1-1/4" and look for a pump that can deliver the 600-900 gph at about 25 ft of head. You probably should be looking at an external Pan World or Iwaki unless you want to spend huge dollars on one of the German DC pumps.

 

[ecexotics]

imo vectra are good pump but not good for a build like you describe. pumps geared for koi ponds are generally your best bet for head pressure, some having up to 40 feet of head pressure. just make sure it's rated for saltwater so the bearings don't rust. i have one my father had on his 23000 koi pond and i'm using it for closed loop. makes me think how much money / hair pulling i could have saved

 

[JoshH]

Shouldn’t a 3100gph pump preform better then a 2000gph in flow ?

Not necessarily, the main issue here is friction loss in your case. The faster water flows, the more friction it creates and trying to flow 3100gph through a 3/4" pipe is really not going to end well. Even 2000 gph is well beyond what the Vectras could handle.

Is my head pressure that bad that either of these pumps can’t preform higher then 180gph ?

Yes.

should I replace return line to 1” even if the tank has 3/4” return nozzles?

Realistically you should be looking into the 1.5-2" return line size and splitting it at the tank to dual returns. However, if this isn't an option, running a 1.5-2" line right up to the bottom of the overflow will absolutely increase your flow as it will greatly reduce the friction loss of your plumbing up to the tank itself. Yes you will still lose some flow from the restriction at the tank but it will be MUCH less than what you're trying to run now....

Reducing the Vectra L2 pump from 1.25 to 3/4” will that cause performance loss

Absolutely.

Just for fun try this online calculator out. It will give you your friction loss numbers and you add those to the total actual height you're trying to pump up to (8') and personally I'm a little shocked you're getting any flow out of that M2 atall....

On-Line Friction Piping Loss

 

[Jackooze]

Unfortunately the vectras don't do well against head pressure. The L2 will flow better, but you would need to upgrade the pipe from 3/4" to 1" or even 1.25".

The problem with just getting a beast of a pump and using the 3/4 is it will use a lot more power than necessary. Upgrading the line will be far cheaper in the long run.

However with all that said, if you are getting a real 180 gph, that is likely just fine for a 65g tank.

If I do replace the 3/4” to 1” or 1.25” line wouldn’t it defeat the whole purpose when I have to reduce it at the tank back to 3/4”? I can’t change the plumbing inside the overflow box.

 

[Jackooze]

Your elevation gain alone is 15 feet of head. Adding the friction losses at probably 2-4 ft and you are all the way back on the curve of the L2 which maxes out at about 21 ft with zero flow. As the backpressure (head) on the discharge of a pump increases, the flow is reduced. The end of curve, zero head flow rate is meaningless - especially in your basement application. Vendors post these values but you rarely can get more than about 50% of the flow even in an ideal set-up.

You will need a much higher head pump. You did not say how much flow you would like to have, but the two 3/4" returns are practically going to limit you to about 600-900 gph total. I would increase the line size to 1" or even 1-1/4" and look for a pump that can deliver the 600-900 gph at about 25 ft of head. You probably should be looking at an external Pan World or Iwaki unless you want to spend huge dollars on one of the German DC pumps.

The Vectra L2 barely fit inside the sump so I am limited to which types of pumps I can use. Unfortunately external is not in the budget because I would have to either drill a whole in this sump or get a new one. I am trying the make the best of my situation. IfI increase the line size it will have to be reduce by the tank so won’t that defeat the whole purpose ?

 

[Jackooze]

imo vectra are good pump but not good for a build like you describe. pumps geared for koi ponds are generally your best bet for head pressure, some having up to 40 feet of head pressure. just make sure it's rated for saltwater so the bearings don't rust. i have one my father had on his 23000 koi pond and i'm using it for closed loop. makes me think how much money / hair pulling i could have saved

I wish I had the room to add a pump like that. Unfortunately I can only add a pump maximum width 5” and length 8”

 

[Jackooze]

Not necessarily, the main issue here is friction loss in your case. The faster water flows, the more friction it creates and trying to flow 3100gph through a 3/4" pipe is really not going to end well. Even 2000 gph is well beyond what the Vectras could handle.



Yes.



Realistically you should be looking into the 1.5-2" return line size and splitting it at the tank to dual returns. However, if this isn't an option, running a 1.5-2" line right up to the bottom of the overflow will absolutely increase your flow as it will greatly reduce the friction loss of your plumbing up to the tank itself. Yes you will still lose some flow from the restriction at the tank but it will be MUCH less than what you're trying to run now....



Absolutely.

Just for fun try this online calculator out. It will give you your friction loss numbers and you add those to the total actual height you're trying to pump up to (8') and personally I'm a little shocked you're getting any flow out of that M2 atall....

On-Line Friction Piping Loss

So if I increase the return line to 1.25” and use the Vectra L2 pump and the. Reduce back to 3/4” at the tank, you think I will gain another 100+ gph ? My goal is to try to get at least 250-300gph

 

[DCR]

I misread your original post. The elevation gain is only 8 ft, so the friction loss is more significant. Yes, going to 1" or 1-1/4" would almost certainly give you an extra 100 gph. It sounds like you also have a flow meter in the circuit (I assume 3/4"). I would upgrade that to a much larger diameter as well as they add a lot of friction loss in the smaller sizes.

 

[Jackooze]

Thank you all for responding with all the great info.

Gathering all this info would I be correct to use the upgraded pump Vectra L2 with 1.25 diameter pipe then reduced to 3/4” by the tank or should I keep the old pump Vectra m1 and increase the plumbing to 1” ?

I am concerned I will do all this work changing the plumbing with little beneficial results.

 

[JoshH]

So if I increase the return line to 1.25” and use the Vectra L2 pump and the. Reduce back to 3/4” at the tank, you think I will gain another 100+ gph ? My goal is to try to get at least 250-300gph

I would increase it to 1.5" if possible first before upgrading to the L2 and see where that gets you.

 

[Jackooze]

I spoke with Ecotech customer service and they said it’s normal to see the same exact gph output from both pumps because of the plumbing and restrictions. They also said even if I switch to a larger diameter pipe and reduced it to 3/4” it will not have a significant affect. So I don’t know what to think.

 

[JoshH]

I spoke with Ecotech customer service and they said it’s normal to see the same exact gph output from both pumps because of the plumbing and restrictions. They also said even if I switch to a larger diameter pipe and reduced it to 3/4” it will not have a significant affect. So I don’t know what to think.

I would increase the diameter of the pipe and start there, it's a pretty cheap way of potentially increasing your flow to what you want. It's a little concerning to hear them say increasing the pipe diameter won't have a significant impact on flow

 

[Jackooze]

I would increase the diameter of the pipe and start there, it's a pretty cheap way of potentially increasing your flow to what you want. It's a little concerning to hear them say increasing the pipe diameter won't have a significant impact on flow

Well they said that it won’t have much impact because it still has to get reduce to 3/4” at the tank. I can’t decided between 1.25 or 1.5.

 

[JoshH]

Well they said that it won’t have much impact because it still has to get reduce to 3/4” at the tank. I can’t decided between 1.25 or 1.5.

The difference is right now the friction loss on the 19 orso feet of 3/4" line is astronomical. Doubling the pipe size will drastically reduce this effect over the length of the pipe. Ofcourse there will still be an issue with reducing at the tank but the restriction will only be at the reduction point and not along the entire length of the pipe...

 

[ca1ore]

Despite the comments from ETM, it does strike me as a bit odd that the L2 does not outperform the M2 … at least by a little. There is no question that the Vectra performs generally poorly with back pressure, mostly because it is designed for flow not pressure. My guess is that moving to larger plumbing, even if the final run cannot be changed, will help with flow. If you decide to try a different pump, the Fluval seas models are not physically large and perform very well.

 

[jda]

You are not going to want to hear this, but if you really need to fight some head, then sell both of those and get a Laguna, Fluval or Mag Drive. You will not likely be able to do much with either of those pumps to get to where you need to go. Drilling a hole in the sump and using a Blueline/PanWorld/Iwaki would be better, but some people do not want an external pump. Vectra and most DC pumps are not the right tool for this job. Sorry.

Red Dragon or Abyzz would get the job done too at an extra cost.

 

[Jackooze]

Despite the comments from ETM, it does strike me as a bit odd that the L2 does not outperform the M2 … at least by a little. There is no question that the Vectra performs generally poorly with back pressure, mostly because it is designed for flow not pressure. My guess is that moving to larger plumbing, even if the final run cannot be changed, will help with flow. If you decide to try a different pump, the Fluval seas models are not physically large and perform very well.

I’m surprised everyone recommends Fluval Sea when it’s max head pressure is 12.1 feet.

 

[Jackooze]

You are not going to want to hear this, but if you really need to fight some head, then sell both of those and get a Laguna, Fluval or Mag Drive. You will not likely be able to do much with either of those pumps to get to where you need to go. Drilling a hole in the sump and using a Blueline/PanWorld/Iwaki would be better, but some people do not want an external pump. Vectra and most DC pumps are not the right tool for this job. Sorry.

Red Dragon or Abyzz would get the job done too at an extra cost.

Yeah it’s a bummer. Trying to figure out what the best options is. I tried searching for Fluval, Mag , and Laguna that provides similar head pressure like the Vectra but I couldn’t find anything over 21ft. Which ones were you describing. My max dimensions is 5”x8” that could fit in the chamber.