Under-sizing your return plumbing can have a negative effect! Do you have good return flow?

[Mike Marsh]

Notes from an actual plumbing engineer.

Easy answer, Get a pump bigger than you need and you can turn it down.

You want 3-5x turnover for your return. so take your tank size x5, then fine a pump that will do TWICE that amount.

If you are pumping up to another floor you have to look at one more thing. Height. Pumps are sized for head pressure, which is in feet or meters. This is how high the pump can push water straight up. You will need to look at a graph (called a pump curve) and make sure the pump will flow the 5x volume that you want at the height you need.

Best practice for piping, Whatever connection size your have on your pumps go one size up for your plumbing. Got a 3/4" outlet on the pump, use 1". Got a 1.5" inlet, use 2".

After 20 years in the hobby here is what I go by for sizing.

Supply:
1/4" - 0-20 GPH
1/2" - 20-250 GPH
3/4" - 250-750 GPH
1" - 750-1200 GPH
1.25" - 1250-1500 GPH
1.5" - 1500-2000 GPH
2" - 2000-5000 GPH

Drains Open flow:
1/4" - Dont
1/2" - 0-30 GPH
3/4" - 30-250 GPH
1" - 250-750 GPH
1.25" - 750-1200 GPH
1.5" - 1200-1800 GPH
2" - 1800-2400 GPH


Drains Siphon flow:
1/4" - Dont
1/2" - 20-250 GPH
3/4" - 250-750 GPH
1" - 750-1200 GPH
1.25" - 1250-1500 GPH
1.5" - 1500-2000 GPH
2" - 2000-3000 GPH

Wow.
I’m in the midst of designing / dreaming a 660 gallon peninsula tank (120” x 48” x 26”) and had planned on 1 1/2” pipes. Also planned for a closed loop. I thought 1 1/2” pipes would be enough.
Weir size can also be a limitation … I found a calculator Weir flow calculator showing a 36” weir effectively actually 18” with 1” height gives 3240 gph …. Just below 5x turnover.

Any thoughts ?

 

[Enderg60]

Depends on your closed loop flow. If youre around 3000 GPH you would be ok with 1.5" BUT personally Id go 2"

Im running 2" on my closed loops but they are 5500 GPH each.

And the weir flow was my downfall on my old 300DD. It could not handle more than 900 GPH, and if you didnt want to see the cross braces in the water you had to turn it down to 400GPH. It worked alright thanks to the closed loop, but yeah that was a major handicap.

 

[Sean Clark]

I'm interested in how you are setup - which peninsula do you have - what are the dimensions? What pump and return outlets - i.e. random flow generators? And did you place outlets through the base of your tank before installing or use the stock ones from the return? I personally feel this might be the best way to provide flow at the far end of a peninsula but involves cutting the glass (scary) and scaping around the outflows (probably not too bad but would have to try and ensure they stay free of debris in a sand bottom tank). We have a 6ft and getting decent varied flow at the far end is a challenge.

We also do not want to 'muddy-up' our far end display panel as it gives a great view through the tank. See my post above - we have 2 MP40s aside the weir about half way up and a XF350 gyre mounted on the weir just under the water surface. I did think about swapping out the MP40s for XF350's mounted vertically but that's a pricy gamble.

The tank is an IM 200EXT (71x30x21). The return pump is a Skims leopard L160. The return outlets are CPR eductors. I originally tried to run four random flow generators on splitters but found that the CPR eductors had way more punch and really get the water moving. The powerhead is a Tunze Stream3 with the "flow rectifier" grill attached which "straightens" out the flow and is designed to push the water longer distances. You can find all of the details under my build thread badge.

 

[Mike Marsh]

Also Pipe Flow Calculator for a gravity fed system (aka overflow) for 1.5 pipe and drop of 4 ft will flow 0.242 cu ft / sec or 1.81 gal/s or 6500 gph.
for a ~ 600 gallon system is greater than 10x turnover. In my planned system , the weir will be the limiting part of the plumbing.

Lastly returns most often end in 3/4 pipe .

 

[Enderg60]

That is if you have a straight pipe out the bottom of your tank in full siphon flow with no elbows. AKA ideal world for doing math problems.

If you want to get into the details, the reason you dont want to expect that much flow out of a 1.5" pipe is, if you are running a siphon for a drain you want an adjustment valve for fine tuning. Valves are accurate for adjustments in the mid range, while also not being potential clog points.

Leave room for error.

 

[Colt13]

I thought my m2 vectra might not cut it for my 210g. I avoided barbed fittings and went with flex pvc. It only stepped down from 1” at the bulkhead of the return line. Insane amount of flow when it’s unrestricted like that. I’m running about 50% and everything is working great.

barbs kill flow, just compare pvc inside diameter to the barbed inside diameter and you can picture how much flow you’re killing.

what is flex pvc? flexible pvc tubing? how'd you connect that without barbs? can you post pics?

 

[Smite]

what is flex pvc? flexible pvc tubing? how'd you connect that without barbs? can you post pics?

I recently swapped sumps. Only picture I can find is just before. Had I been able to eliminate that elbow in the run, the flow would have been crazy on the return.

Here is a close up of a connection. The connect just like PVC.

Tips:
1. You HAVE to use PVC primer on both the flex pvc and fitting just before applying the glue.
2. When you press in your flex to the pvc fitting, 1/4 twist and hold together for at least a 10 count. PVC fittings are tapered, the flex pvc goes in the fitting much easier, so it has to bottom out all the way to get a good connection.
3. since it has to bottom out you cuts need to be pretty precise.
4. It's not as flexible as you think, fairly rigid. I used a harbor freight heat gun to loosen them up for bends and also to take the bend out that forms from being in the roll when new.

It makes plumbing a breeze really. Specially if you have runs that aren't straight shots. I feel like they also reduce stress on the bulkheads from plumbing imperfections. If I were ever to do an external overflow again, these would be a must. Plan to strap them, at 80F and with water weight they will sag over time.

Hope that helps. Oh Lowe's sells it by the foot in the plumbing/tubing isle.

 

[Colt13]

I recently swapped sumps. Only picture I can find is just before. Had I been able to eliminate that elbow in the run, the flow would have been crazy on the return.

Here is a close up of a connection. The connect just like PVC.

Tips:
1. You HAVE to use PVC primer on both the flex pvc and fitting just before applying the glue.
2. When you press in your flex to the pvc fitting, 1/4 twist and hold together for at least a 10 count. PVC fittings are tapered, the flex pvc goes in the fitting much easier, so it has to bottom out all the way to get a good connection.
3. since it has to bottom out you cuts need to be pretty precise.
4. It's not as flexible as you think, fairly rigid. I used a harbor freight heat gun to loosen them up for bends and also to take the bend out that forms from being in the roll when new.

It makes plumbing a breeze really. Specially if you have runs that aren't straight shots. I feel like they also reduce stress on the bulkheads from plumbing imperfections. If I were ever to do an external overflow again, these would be a must. Plan to strap them, at 80F and with water weight they will sag over time.

Hope that helps. Oh Lowe's sells it by the foot in the plumbing/tubing isle.

wow, surprised ive never seen this done before, thanks for the detailed response i might actually do this

 

[Harpo]

I agree with the Posts above.....Return flow doesn't have to be much these days since we have plenty of choices for In-Tank powerheads. A slower return flow can be better due to longer contact time in Sump/Skimmer.

My sump is in basement and Tank is on 1st floor. Lots of height and my plumbing runs thru walls, ceiling, and nd needs to turn a few times.

I don't like hard-plumbling since it can be noisy (buzz, rattle), and hard to get perfect runs with elbows and gluing process. 90 degree turns reduce flow somewhat so better to have gentle angles.

This isn't as pretty as the GLUE PVC pipe/elblow, etc.....but works better for me. Equally Kink free.

For the Pump to Tank plumbing, I used similar type of hose by not as big of a diameter.

https://www.halfoffponds.com/Half-Off-Ponds-Kink-Free-Vinyl-Hose-1-x-100-p/kf1x100.htm

This is the type of hose I used for return-drain out of tank. Smooth on inside for better flow and quieter too. Works like a charm.


BOTH hoses are easily removable for a cleaning if needed to remove (years of calcification on inner walls)

I prefer the flexible PVC, sometimes referred to as jacuzzi tubing. Adding a union to the joint will also help with alignment & flexibility. Opps, missed smites post above.

 

[OrlandoAIOReef]

Did you know that "under-sizing" your return plumbing can have a negative effect because it restricts the return flow of water back into your aquarium?

Us non-plumber types tend to think of a water hose without a nozzle. What do you do if you want the water hose to spray a long distance and with more force? Kink it up a little right!? Well it doesn't really work that way with return plumbing. Your return pump will struggle with pushing more volume of water through the pvc and back into your reef tank. A return pump is not really designed to be a source of strong flow inside of your aquarium. If you want to get a more forceful spray back into your tank though you need to open the flow through the pvc and then use a specially designed return nozzle to do the rest.

Do you have problems with getting enough water flow from your return pump back in your display tank?

PLEASE SHOW US A PHOTO OF YOUR RETURN PLUMBING FROM YOUR PUMP!

image via @Firemanreefkeeper

So how much does it restrict? Is it equal to the size? Like putting a 3/4” fitting on a 1&1/ 2” output reduce flow by half?