Best line width from return pump… head loss

[jandree22]

The Iwaki 30RLT I just bought has ¾” MPT in and ¾” MPT out. It’ll be pushing water out of the basement sump into the display. My question is, would I benefit from expanding the width of that line to 1” or perhaps even more, or, will I see no benefit above ¾” width as that’s the outlet size of the pump. Or, alternatively, am I adding unnecessary head pressure by having a wider than spec width line (ie, more water volume in the line = heavier load to move)?

Furthermore, when I “T” or “Y” off the line into the display, should I reduce the pipe diameter at all or keep it the same as before the split?

 

[Anonymous]

First off larger pipe will give you less flow losses. Second the lift is the lift and the pressure at the pump will not vary based on pipe diameter.

Looking at what you have and making some educated guesses. You probably have 14ft of lift from you sump to the top of your tank. I am assuming your sump is on the basement floor, 8ft ceiling in the basement, 16" floor joist, 4 ft to the top of your tank from the floor. Before flow losses you will have about 250gph (4.2gpm) from your pump. losses for that flow rate per 100 ft of pipe is 5.7 ft in 3/4" pipe and 1.7 ft for 1" pipe. COnsidering you will have about 20ft of pipe total your estimated losses will be about 1.14 ft if you use the 3/4" pipe and .34 ft is you use the 1". Flow for each will be right about 150 gph if you use 3/4" pipe and near 200 gph if you use 1" pipe.

You can reduce the pipe size after T or Y is you like, just don't go more than one pipe size.

I am going to guess you are putting up a 120 or somthing along those lines. IMO you do not have enough flow. Consider getting the sump off the floor (if that is where it is) and getting a larger pump. Getting the sump 4ft off the floor you will pick up about 200 gph in either case.

 

[Anonymous]

If it is confusing let me know. Ask specific questions and I can better cover the issue..

 

[jandree22]

Wow, thanks for all that analysis. Few clarifications… first, it’s only a 75g tank, unfortunately . I plan to mount the sump 3’ to 4’ off the ground (still have to build a stand for it, so the jury’s still out). The ceiling isn’t even 8’, so including the joists, I’ll still say 9’ worst case scenario. Top of tank is approx 4’ off the floor. So 9’ – 3’ + 4’ = 10’ of lift. According to this flow chart (see 30RT, the 'L' just indicates UL listing), @ 10’ of head it’s still around 420gph, as the RLT is meant for pressure applications.

However you still answered my question really well with difference between ¾” and 1”. 20’ is overestimating it a bit, but with the addition of bends and valves it’ll still be a few extra feet of flow loss. I still can’t wrap my head around the fact that the load on the pump isn’t affected by the volume of water included in the vertical section of pipe, but I’ll take your word for it I’ll definitely go for the 1” diameter the entire way. thanks again!

 

[Anonymous]

Good post Marky Mark!

 

[Anonymous]

I still can’t wrap my head around the fact that the load on the pump isn’t affected by the volume of water included in the vertical section of pipe, but I’ll take your word for it.

That is because you are thinking total weight, not pressure (psi). The pressure, in ft, at any depth in the water column is equal to the depth you are taking the measurment, for freshwater. For saltwater you multiply the depth by the SG.

 

[Anonymous]

Good post Marky Mark!

Thanks. It helps that I use to design pumps and piping systems for a living. I know where the charts are and how to use them.

 

[jandree22]

Good post Marky Mark!

It helps that I use to design pumps and piping systems for a living. I know where the charts are and how to use them.

heh, in that case, I didn't mean to insult your intelligence

I was actually kind of amazed with those figures you calculated for flow loss between 3/4" and 1"

 

[Anonymous]

Good post Marky Mark!

I know where the charts are and how to use them.

heh, didn't mean to insult your intelligence

I was actually kind of amazed with those figures you calculated for flow loss between 3/4" and 1"

You did not insult me in any way, shape or form. I did not really calculate much. A lot of this stuff you can look up on charts and get close approximations without ever picking up a calculator.

For you information flow losses are a function of the fluid velosity squared. So when you increase the pipe diameter you increase the cross sectional area (flow area) and the flow velosity for the same volume flow goes down. Therefor the losses go down. Double the area and the losses go down by a factor of 4.

 

[jandree22]

I actually think I understand that... basically with a narrow channel, the flow is forced to move faster generating more friction against the channel, translating into lost energy.

 

[Anonymous]

Basically yes.

 

[jandree22]

10-4, thanks again for your help w/this

 

[liquid]

You might find this:

http://www.advancedaquarist.com/2007/5/aafeature2

and the installable program helpful linked into that article.

Shane

 

[das75]

know any calculator that can handle (are how do existing handle) different size of pipe.

Example running from the pump to the tank in 2", 1" bulkhead in the bottom of the tank, then last 2 feet as 1"

 

[jandree22]

the key here that I was wondering about is if the 'weakest link' rule applied to plumbing. specifically, since it's leaving the pump through a 3/4" outlet, is adding 1" pipe for the rest of the way going to even matter?

and the answer I got is yes, due to continued reduction of friction with the wider diameter channel. makes sense now after it was explained in such detail by waz

thanks for the AA link, none the less... I'll give 'er a read through.

 

[Anonymous]

know any calculator that can handle (are how do existing handle) different size of pipe.

Example running from the pump to the tank in 2", 1" bulkhead in the bottom of the tank, then last 2 feet as 1"

It is easy. Piping in series has the same flow rate. It is a itertave process tho. First shot should get you close enough since we are not talking large head losses or long runs. Here is how it works.

First take the flow rate for the static lift (top of sump water level to top of tank water level).

Look at a chart like this http://www.plumbingsupply.com/flowchart.html for each pipe size and note the losses for that run length. Notice the losses for the chart I put up is for 100 ft of pipe.

Add the losses together and that is the total losses of the run at that flow rate.

Add those losses to the static lift and repeat to get a better answer. you will get a convering answer after a few tries. For me I just check it once for fish tank stuff.

 

[Anonymous]

the key here that I was wondering about is if the 'weakest link' rule applied to plumbing. specifically, since it's leaving the pump through a 3/4" outlet, is adding 1" pipe for the rest of the way going to even matter?

and the answer I got is yes, due to continued reduction of friction with the wider diameter channel. makes sense now after it was explained in such detail by waz

thanks for the AA link, none the less... I'll give 'er a read through.

It's not really a weakest link thing. If you have a run of multiple pipe diameters you have to figure the losses for each section then add them together.

 

[Anonymous]

Look at a chart like this http://www.plumbingsupply.com/flowchart.html

Mark, check the number for 10 GPM with 1/2" pipe. It says 82.02. Does that mean that the head loss from friction would be nearly as much as from the static lift? If so, that's pretty amazing that you lose that much due to friction.

 

[Anonymous]

Look at a chart like this http://www.plumbingsupply.com/flowchart.html

Mark, check the number for 10 GPM with 1/2" pipe. It says 82.02. Does that mean that the head loss from friction would be nearly as much as from the static lift? If so, that's pretty amazing that you lose that much due to friction.

That is for 100ft of pipe in any direction. At 10gpm in 1/2" pipe the water will be haulin' a$$.