Return line pipe diameter

[Miker79]

I’m designing the plumbing for a new sump, I plan on using a vectra m1 pump which has a 3/4” outlet. My question is should I bush it to 1” and then bush it down to 3/4” before the bulkhead? I wonder if I’m needlessly making it more complicated then it needs to be or is there a real benefit to upsizing the pipe diameter.

Mike

 

[Crabs McJones]

Welcome to R2R! Personally I would keep the piping 3/4 all the way through if that is the size of the outlet on the pump .

#WelcometoR2R

 

[DCR]

It does not make sense run a 2000 gph pump like an M1 with 3/4" pipe unless you plan on turning it down to 300-400 gph. The S1 would be a better fit. You should generally expand at least one pipe size or even two from the pump discharge to get the full capacity of the pump.

 

[roberthu526]

The flow rate is mainly determining Ned by the smallest diameter in line so expanding to 1” won’t help.

 

[TLeTourneau]

I took the 1.25" from my pump down to 1" for the manifold that has connections for reactors and the return to the tank. I went with 1" because that is the size of my flow sensor. The return to the tank is 5/8".

 

[Reeceblse]

What I don’t understand is that at 100psi, 3/4” pvc has a max flow rate of around 1400gph. How does a company flow rate their pump at 2200gph with a 3/4 barb as the outlet?

 

[KrisReef]

What I don’t understand is that at 100psi, 3/4” pvc has a max flow rate of around 1400gph. How does a company flow rate their pump at 2200gph with a 3/4 barb as the outlet?

zero head =1400gph. Not a very useful number really.
What do they give at 4' for that pump. That number is more like what you should expect using the 3/4" return pipe.

 

[KStatefan]

The flow rate is mainly determining Ned by the smallest diameter in line so expanding to 1” won’t help.

Up sizing the pipe will reduce the friction loss in the pipe.

 

[roberthu526]

Up sizing the pipe will reduce the friction loss in the pipe.

Yes but since it’s 3/4” right out of the pump expanding it to 1” isn’t really going to help that much. I could be wrong though as I have never done any experiment.

 

[KStatefan]

Yes but since it’s 3/4” right out of the pump expanding it to 1” isn’t really going to help that much. I could be wrong though as I have never done any experiment.

It depends on the velocity of the water the higher the velocity the more it will help.

 

[DCR]

Pumps are often designed with restricted discharge nozzles for better efficiency at higher heads. You should not assume that is the correct line size for your return. The choice of line size is a compromise between pump power consumption and the cost of the piping. I have sized lines throughout my career as an engineer and I would not generally use a 3/4" pipe for more than about 300-400 gph. You can certainly get more flow than that with higher head, but you are consuming a lot of extra power due to the increased friction loss. The pressure loss goes up with the square of the velocity, so it ramps up quickly. Aquarium pumps are generally not very high head and cannot overcome restricted piping. It pains me to see people paying several hundred dollars for these DC pumps, and then using undersized piping which forces them to run at higher speeds, thereby negating much of the benefits of the pump. As a rough rule of thumb, I would use 3/4" up to 300 gph, 1" up to 600 gph, 1-1/4" up to 1200 gph, and 1-1/2" up to about 1800 gph. If you do this, you will keep your frictional losses to no more than about 2-4 feet of head in most applications. Add your elevation gain and choose your pump for the flow and total head. Be wary of any of these flow killing, high velocity, discharge nozzles. For an M1, you should be able to achieve up to about 1000-1200 gph at max speed in most systems, but you would need to use at least 1-1/4" pipe.

 

[ca1ore]

What I don’t understand is that at 100psi, 3/4” pvc has a max flow rate of around 1400gph. How does a company flow rate their pump at 2200gph with a 3/4 barb as the outlet?

You would have to check the pump literature to be certain, but if memory serves the maximum flow claimed for the Vectra pumps is based on the native threads ..... which are 1 1/4" for the M1. Putting the 3/4" collar on will significantly reduce the maximum flow even with zero head.

The degree to which you can retain native (get rid of the 3/4" fitting) 1 1/4" throughout the length of the return will help immensely. I run my M1 as a closed loop through 1 1/4" flex PVC and get very close to 2,000 gph with the pump at 100%.

 

[piranhaman00]

Bump!

For a new tank I am planning I was thinking about doing 1" pvc. However, the output of the pump and using locline will be be 3/4". Is going from 3/4" (pump) expand to 1" immediatly, and then run 1" all the way to the bulkhead before it is reduced again to 3/4" add any benefit? Or am I better off just doing 3/4 the whole way to make it easier? What gph can you get through 3/4 vs 1"?

Thanks,

 

[NeonRabbit221B]

Your bottle neck will be 3/4" so this will have no added benefit that I can think of.

 

[piranhaman00]

Your bottle neck will be 3/4" so this will have no added benefit that I can think of.

Thats what I figured as I am planning.

What return options for 1" bulkhead are there without loc line?

 

[KrisReef]

Larger pipe lowers friction that allows more flow through the pipe, even with the restriction on both ends.
Is it significant,? :?

 

[diverpat]

I’d go with the 1inch if you are questioning it. Don’t base the pipe size off of the pump outlet. The reduced pipe size on the downstream side will just continue to add restriction and decrease flow. The flow restriction is cumulative over the entire length of pipe, not just the smallest restriction.

 

[piranhaman00]

I’d go with the 1inch if you are questioning it. Don’t base the pipe size off of the pump outlet. The reduced pipe size on the downstream side will just continue to add restriction and decrease flow. The flow restriction is cumulative over the entire length of pipe, not just the smallest restriction.

Thanks for the replies.
i am going to do 1” all the way to bulkhead and reduce to 3/4 for loc line thanks

 

[piranhaman00]

What is max gph through 3/4” pvc? I see the charts, what psi do we expect in our return plumbing?

 

[KStatefan]

What is max gph through 3/4” pvc? I see the charts, what psi do we expect in our return plumbing?

The flow chart of the pump will give you the pressure that the pump is designed for. Yoiu will have to convert head pressure to psi. feet head / 2.3 = psi