Head pressures, are your elbows making a difference?

[randyBRS]

Hey guys! In this week's installment of BRStv Investigates we take a look at the differences in flow loss between 45 and 90 degree elbows.

It's a topic that we've all seen dozens of posts about, so I can't wait to hear what you guys think!

What have you read, heard, or know about plumbing fittings and the loss of flow?




-Randy

 

[Drakonis]

Good to see lack of difference proven but for me this raised the question that is common to most of our systems. splitting output from a pump to two or more outlets, what is the impact of where/how this is done on GPH?

 

[LJ22s]

Randy,

Would you guys be willing to do an episode on algae scrubbers? I'm particularly looking at the drop units from Santa Monica to put in my IM Fusion 30. I don't see much information on benefits/negatives. Thanks

 

[pelphrey]

Randy,

Would you guys be willing to do an episode on algae scrubbers? I'm particularly looking at the drop units from Santa Monica to put in my IM Fusion 30. I don't see much information on benefits/negatives. Thanks

BRS Did this video

Week 48: Solving your reef tank's algae problems forever | 52 Weeks of Reefing #BRS160

 

[randyBRS]

Good to see lack of difference proven but for me this raised the question that is common to most of our systems. splitting output from a pump to two or more outlets, what is the impact of where/how this is done on GPH?

Absolutely! I'm guessing that the GPH drop would be much more significant than an elbow. Hopefully we can test something like this when we get our hands on the Neptune FMK!

Randy,

Would you guys be willing to do an episode on algae scrubbers? I'm particularly looking at the drop units from Santa Monica to put in my IM Fusion 30. I don't see much information on benefits/negatives. Thanks

Hey @LJ22s ! I know for sure ATS designs and functionalities are on the board for BRStv Investigates. I'm just as interested because I use one of the Santa Monica floating ATS on my tank at home!

 

[revhtree]

Great video and informational!

 

[rayn]

Great video! What I learned there is that no matter how you plumb your tank, with 45's or 90's, the rated pressure doesn't seem to be enough!

Maybe the scicce 10 would have done better with 1.5" pipe, but only one came to the flow stated.

 

[Tklb]

An alternative test would be 2 90 elbows vs. 2 45s. basically from the return pump to the bulkheads for the returns. Also the 45s farther apart should make more of a difference. Right next to each other they act more like a 90.

 

[randyBRS]

Great video! What I learned there is that no matter how you plumb your tank, with 45's or 90's, the rated pressure doesn't seem to be enough!

Maybe the scicce 10 would have done better with 1.5" pipe, but only one came to the flow stated.

I was honestly surprised myself, especially from all of the advice about 45s vs 90s I read about as a beginner. That sort of "rule of thumb" has stuck with me ever since.

An alternative test would be 2 90 elbows vs. 2 45s. basically from the return pump to the bulkheads for the returns. Also the 45s farther apart should make more of a difference. Right next to each other they act more like a 90.

I wish we could have extended this into other fittings also. I'd be interested in the impacts from Tees, reducers and bulkheads. :)




What are your thoughts about fittings and their effects on drain lines?

-Randy

 

[McArcher]

If you are concerned about head loss and the amount of flow you are getting out of your pumps, I would be more concerned about pipe size. There is no way you can plumb your tank without using fittings. Just plan appropriately and use as few fittings as possible and use flexible pvc to make turns if you can get away with it. I know it looks cool and more professional, but there is roughly a 10% difference in the ID of 1" Schedule 80 pipe vs. 1" Schedule 40 pipe. Head loss is related to the square of velocity and the smaller ID if the Schedule 80 pipe means the velocity is higher, thus the head loss is higher. If you want a cool look, use colored Schedule 40 instead of Schedule 80.

 

[McArcher]

Good to see lack of difference proven but for me this raised the question that is common to most of our systems. splitting output from a pump to two or more outlets, what is the impact of where/how this is done on GPH?

Actually, it is not as much as you would think. When you split the flow, you are pushing less water through the pipe so the velocity goes way down. Velocity is the enemy when you are fighting head loss. My suggestion would be when you split flow, do not use reducing tees. Keep the pipe the same size throughout and only neck down when you get to the return head.

 

[pfoxgrover]

So what about sweep 90's? Are they expected to perform no better than 2 - 45's?

 

[pfoxgrover]

I have not seen sch 40 colored PVC. I always thought sch 80 was overkill but I am looking for that cool look.
Is that something that can be easily found?

 

[McArcher]

BRS sells colored Schedule 40

 

[pfoxgrover]

BRS sells colored Schedule 40

ahh, I was thinking of the fittings. Still, sch 80 fittings are overkill but, the gray looks much better than the white.

 

[dnyceli]

As always another great and informative video. Thank you all at BRS for putting in so much leg work for the rest of the community. I've been a long time follower of your videos. It would be so cool too have a pair of the BRS clown off springs in my tank =)

 

[TylerS]

Good video! I really enjoy this series.

So I'm a self professed nerd and also a mechanical engineer who can crunch the theoretical numbers on this. I had a calculator I made for sizing a basement return pump and I plugged this setup into it. The theoretical loss difference between the two options tested at 950 gph is only 0.12 feet (and the calculations aren't that accurate anyway, only within 10% at best). Theoretically two 45 are worse than a single 90, and there's 3 extra joints which also have a small loss associated with them. A long radius (1.5 x D) 90 degree turn is better than both options tested (by almost a half a foot), but hard to find in schedule 40 or 80. If only there was someone around here who could source long radius 90's in schedule 40 for a decent price ;).

The biggest affect to head loss by far is pipe diameter, and there is absolutely nothing wrong with upsizing the return line. So if your pump outlet is 1" you can run a short length of 1" pipe and then upsize it to 1.5" for the rest of the return for "free" extra flow! This is a big deal for basement sumps and long return lines. Not such a big deal for 5' runs from directly under the tank. For reference, my future basement sump return line head loss drops from 15 ft to 12.5 ft if I upsize the return line from the pump outlet of 1.5" to 2". This is an extra 300 gallons an hour of flow for free in my case. People also need to make sure they aren't downsizing the returns through the bulkhead and locline into the tank (if they get a choice). Even just a 1' run of locline that's to small of a diameter can cause a huge reduction in flow.

If you guys have any questions ask away!

I was honestly surprised myself, especially from all of the advice about 45s vs 90s I read about as a beginner. That sort of "rule of thumb" has stuck with me ever since.

I wish we could have extended this into other fittings also. I'd be interested in the impacts from Tees, reducers and bulkheads. :)

What are your thoughts about fittings and their effects on drain lines?

-Randy

Just make sure your drain line is over sized a little and it really doesn't matter. With return lines you're paying extra for loss by losing flow or having to buy a bigger pump so it's worth it to do a little optimization. With drain lines there's no consequence based on your fittings unless you undersize it. The chart on this page is a good reference for drain line sizing http://www.reefaquarium.com/2012/aquarium-plumbing-basics/

Good to see lack of difference proven but for me this raised the question that is common to most of our systems. splitting output from a pump to two or more outlets, what is the impact of where/how this is done on GPH?

It's small. As @McArcher mentions, don't use tee's with a reduction on both outputs (one of the outlets can be reduced if you purposefully want lower flow in that branch). Also, you should have the branch where you want the most flow to go to be the straight through branch (which is kind of obvious I think). If the flow going into the T is 500 gph, the flow coming out the two sizes added together will be pretty close to 500gph.

I've always wondered what's really the optimal return flow "turnover" rate. Is is 10x tank volume, 5x, 2x? As you increase from 2x and higher there's a huge cost associated with the increased flow in both a larger pump being required, and more electricity to run the pump. Testing on this would be really interesting to me. Start on an established tank that's doing well and reduce the turnover 1 month at a time or so until there's a noticeable negative effect (who's going to volunteer to potentially trash their tank though o_O). I would guess the optimal flow rate would be the lowest rate that keeps the sump and tank homogeneous (the same). You could measure differences between the sump and tank, with the target of keeping the two relatively close (temp, dissolved oxygen, nitrate & phosphate, ph, dkh, etc.). But maybe that's not necessary and even lower turnover rates than that could be ok if you keep the display tank in the "target zones" (so up the temperature in the sump so display tank is at it's target temp).

 

[pfoxgrover]

Good video! I really enjoy this series.

A long radius (1.5 x D) 90 degree turn is better than both options tested (by almost a half a foot), but hard to find in schedule 40 or 80. If only there was someone around here who could source long radius 90's in schedule 40 for a decent price ;).

This is the test we need. I have never heard of using 2 45's together, but I was planning on paying extra for the sweep 90's on my new build. I am interested if that is a waste of money or not?

 

[TylerS]

Or flex line with no sharp bends.

 

[tigé21v]

I've read many times over the years to increase your unions and valves by at least one size because they are flow restrictors. I cannot ever recall coming across info recommending to do the same for 90's and 45's. Anyone know if this would have a measurable impact?
Also, does chamfering the inside of the pipes have a noticeable effect?
Regarding sweeps- would you be better off to use flexible pvc (or bend your own pvc) if a sweep was not an option? It seems flex pvc turns, and bent rigid pvc turns, are rarely if ever circular. A cross section of the said turns has an oval shape.