Pipe size for Vectra M2 going up

aquaticlog · May 3, 2022

I am plumbing my aquarium on the main floor to the sump that's in the basement underneath it (basement ceiling is standard 8 feet) + say another 5-6 feet of the aquarium height. Do I go with 1'' or 3/4'' pipe for the return? I want to maximize the flow, but my understanding is limited on what is the right thing to do here.

Experts, please advise.

ChrisRD · May 3, 2022

Assuming you want as much flow as you can get at the tank I would stick with 1" diameter pipe. The smaller diameter piping will create a significant amount of additional "friction" loss that will reduce flow quite a bit. It's an exponential thing...so the friction losses increase quickly as pipe diameter goes down.

blaxsun · May 3, 2022

That's 14' plus another 1' for every 90-degree bend. Assuming 15' (minimum), your flow will be 400Gph (max) @100% speed. Is that enough? Unless you're planning to upgrade the pump to run more than 1,400Gph (revised), you probably don't need more than 3/4".

aquaticlog · May 4, 2022

Interesting. So it does sound that if I'm running new plumbing I might as well go for a 1'' to maximize the flow (or run the pump at less than 100). From what I've been reading - there's no reason to chose 3/4'' over 1'' in my case (DC pump)

aquaticlog · May 4, 2022

blaxsun said:
That's 14' plus another 1' for every 90-degree bend. Assuming 15' (minimum), your flow will be 400Gph (max) @100% speed. Is that enough? Unless you're planning to upgrade the pump to run more than 1,400Gph (revised), you probably don't need more than 3/4".

This would be more than enough (400 gph), but if the pump will have to work less with 1'', does it make sense to run it with 1''?

I'm also thinking of doing two overflow runs that are also 1'' (Herbie), does that make sense or do I need to go at 1.25? I can't see how 15' pipe up at 1'' will saturate even 1'' down.

blaxsun · May 4, 2022

aquaticlog said:
This would be more than enough (400 gph), but if the pump will have to work less with 1'', does it make sense to run it with 1''?

I'm also thinking of doing two overflow runs that are also 1'' (Herbie), does that make sense or do I need to go at 1.25? I can't see how 15' pipe up at 1'' will saturate even 1'' down.

I just looked at the performance chart based on vertical head height. Manufacturers typically don’t go into specifics on what diameter of pipe they base this on, but we can assume 1/2” to 3/4” as this is typical for most returns.

I don’t necessarily agree that a 3/4” pipe will cause more friction than a 1” pipe, and based on the height (15’) I would only add that the pump has a higher volume of water to push.

ChrisRD · Jun 18, 2022

Sorry for the late reply...didn't notice this thread was still going. It might not be useful now for the OP but in case someone digs this up in a search...

Pump curves don't assume a pipe size...and the plumbing size can play a significant role in the output of the system. To determine where you will be on the pump curve you have to calculate the total dynamic head. That is basically the sum of gravity head (i.e. how far you are lifting vertically) + the friction losses from the plumbing. If you plug in your info from your plumbing configuration to an online calculator you can get an idea of how much those losses will be.

Something like this:
https://pentairaes.com/pump-calculator

Assuming maybe 20' of total piping, a couple of 90s and a ball valve / union...in this case (15' lift) you'll likely have very little friction loss (maybe 0.7 feet) with 1" plumbing so you would probably get pretty close to the 400 GPH number shown on the M2 pump curve at 15' of total head.

See pump curve here:

VECTRA M2 DC RETURN PUMP (2000 GPH) - Mobius

VECTRA S2, M2 & L2 RETURN PUMP EcoTech Marine has set new standards for equipment in saltwater aquariums. The Vectra is no exception. The world’s smartest return pump can be run on a schedule, wirelessly give you updates on the operation and be automatically configured to work with your...

premiumaquatics.com

If you go to 3/4" plumbing you'll add noticeable friction loss (probably close to 2 feet) so there will be an impact on total flow. You have to play around with the calculator iteratively to find the actual flow number since as you add friction loss you're reducing flow...but you get the idea.

The short version...in this configuration with 1" plumbing I would expect to see close to 400 GPH at the discharge...with 3/4" plumbing I would expect it to be maybe around 300 GPH. Whether that is significant or not I guess depends on how much flow you want.

A good rule of thumb is to look at the output fitting size on the pump. That is usually a good starting point for plumbing size if you're trying to get the most out of the pump. In this case the M2 has a 1" output fitting...

HTH