Semi advanced plumming question

[Cornerboy]

I'm wondering if it would be possible to have two pumps feeding the same return line. I've been watching brstv and appreciating the current talk of having multiple return pumps to prevent disaster in the event of pump failure.

My situation is that my sump and refugium are 20 feet away in the next room and I would really rather not run two sets of return pipes across the bedroom wall. After listening to two pump manufacturers' videos I decided to over size the return line and used one and a quarter inch PVC pipe.

So my idea is to take two 3/4 inch lines going from multiple return pumps into a 1 1/4 x 3/4 Y and into the 1 1/4 inch PVC pipe. I would put backflow valves just before the Y. The pumps are similar in terms of gallons per hour and capacity for head pressure. So if there are any fluid dynamics engineers or better yet a seasoned plumber who would like to contribute their thoughts I would greatly appreciate it.

I'm leaning towards just using one pump and keeping the other as a spare but I'll Stand By and hear what people have to say.

Thank You!!

 

[Ridgeway]

You could simply connect them inline, ie outlet of pump 1 goes to inlet of pump 2 etc.

 

[Cornerboy]

You could simply connect them inline, ie outlet of pump 1 goes to inlet of pump 2 etc.

I didn't know that even worked. Have you done that? I would think the pumps would hinder each others performance inline, but i don't know diddly ; -)

 

[JLowder]

You could simply connect them inline, ie outlet of pump 1 goes to inlet of pump 2 etc.

This won’t work. The 2nd pumps performance will absolutely be hindered.

 

[JLowder]

I'm wondering if it would be possible to have two pumps feeding the same return line. I've been watching brstv and appreciating the current talk of having multiple return pumps to prevent disaster in the event of pump failure.

My situation is that my sump and refugium are 20 feet away in the next room and I would really rather not run two sets of return pipes across the bedroom wall. After listening to two pump manufacturers' videos I decided to over size the return line and used one and a quarter inch PVC pipe.

So my idea is to take two 3/4 inch lines going from multiple return pumps into a 1 1/4 x 3/4 Y and into the 1 1/4 inch PVC pipe. I would put backflow valves just before the Y. The pumps are similar in terms of gallons per hour and capacity for head pressure. So if there are any fluid dynamics engineers or better yet a seasoned plumber who would like to contribute their thoughts I would greatly appreciate it.

I'm leaning towards just using one pump and keeping the other as a spare but I'll Stand By and hear what people have to say.

Thank You!!

As long as you install the check valve and do the maintenance, you will be fine.

 

[chefjpaul]

You could simply connect them inline, ie outlet of pump 1 goes to inlet of pump 2 etc.

Hmmmmm.... wonder if thats in the warranty notes.

 

[Sleepydoc]

What pumps/what kind of flow were you looking for, and what is the length/head loss of your plumbing? You should definitely put check valves in line, but if you don’t properly size the plumbing you’ll end up wasting a lot of energy fighting head loss. Run the numbers, but it may be worthwhile upsizing to 1.5”

 

[DanP-SD]

It’ll work but a couple caveats to consider: first, the Y should eliminate the need for check valves in normal operation (but not in the hopefully unusual situation where one pump is running and one is not). The advantage to running without the check valves is that when you power off both, you’ll quickly know whether your sump handles the backflow. Better to know that right away.

Second, even with the Y and the use of proper diameter pipes, when the two flows meet in the Y, there will be a lot of turbulence and some possible back pressure assuming proper sized pipes (see below). That will decrease total flow somewhat and will create noise. I think it would be quieter and more efficient to run two separate return pipes. It would be quieter and would move more water. The additional efficiency might even let you get enough flow to use slightly smaller pumps, which would be quieter still.

Third, if you go with your plan, do run the numbers. A 1.5” pipe handles a lot more water than two .75” pipes. I believe a 1.25 does as well. The issue when you converge two pipes into an oversized pipe is you create a vacuum in the pipe — or at least a source of negative pressure. In fact, this is exactly how a Venturi works - rapidly expanding the volume the water has to fill so it draws air in. You won’t have a source of air so I’m not sure what the water will do to respond to the negative pressure. I suspect you’ll create a lot of turbulence and uneven flow but it may be temporary until the pressure reaches equilibrium. I haven’t run this set up to test it so this is somewhat speculative.

Bottom line for me is I’d run two separate returns through two separate lines. This also lets you direct each to a different part of the tank, which creates better water movement.

 

[Cornerboy]

What pumps/what kind of flow were you looking for, and what is the length/head loss of your plumbing? You should definitely put check valves in line, but if you don’t properly size the plumbing you’ll end up wasting a lot of energy fighting head loss. Run the numbers, but it may be worthwhile upsizing to 1.5”

Sleepydoc, I got the Sicce Syncra 3.5 which is 660 gph. The second pump is a yet to be determined DC pump. I would do the math, but I've been told conflicting things and this is my first time trying to calculate it. Actually I should go back and look at those charts now. I think I have a better idea then when I was looking at them before . I'm figuring about 11 feet of head pressure.

The tank has a 1 inch and a three-quarter inch hole drilled in the bottom and that's it. It says it's tempered glass so even if I ran two lines I don't think there be a good way to get into it. I want to use the canopy that it came with which is nice.

I'm shooting for about 500 gallons an hour. The initial plan was to use the 3.5 to get started cycling the tank and keep it later for a backup. I'll have a better idea of which pump I might want to go with after I see how this one performs

 

[Cornerboy]

It’ll work but a couple caveats to consider: first, the Y should eliminate the need for check valves in normal operation (but not in the hopefully unusual situation where one pump is running and one is not). The advantage to running without the check valves is that when you power off both, you’ll quickly know whether your sump handles the backflow. Better to know that right away.

Second, even with the Y and the use of proper diameter pipes, when the two flows meet in the Y, there will be a lot of turbulence and some possible back pressure assuming proper sized pipes (see below). That will decrease total flow somewhat and will create noise. I think it would be quieter and more efficient to run two separate return pipes. It would be quieter and would move more water. The additional efficiency might even let you get enough flow to use slightly smaller pumps, which would be quieter still.

Third, if you go with your plan, do run the numbers. A 1.5” pipe handles a lot more water than two .75” pipes. I believe a 1.25 does as well. The issue when you converge two pipes into an oversized pipe is you create a vacuum in the pipe — or at least a source of negative pressure. In fact, this is exactly how a Venturi works - rapidly expanding the volume the water has to fill so it draws air in. You won’t have a source of air so I’m not sure what the water will do to respond to the negative pressure. I suspect you’ll create a lot of turbulence and uneven flow but it may be temporary until the pressure reaches equilibrium. I haven’t run this set up to test it so this is somewhat speculative.

Bottom line for me is I’d run two separate returns through two separate lines. This also lets you direct each to a different part of the tank, which creates better water movement.

Thanks DanP!! Good points. Thinking

 

[Cornerboy]

As long as you install the check valve and do the maintenance, you will be fine.

Thanks JLowder! The longer I stay on the drawing board the longer I can avoid getting my hands dirty. ;-)

 

[realest20]

I watched the same episode and consider the same idea. I have only 1 return pipe. I would have to add a flow meter then use check valve at the outlet of each pump to make it work. Then program my apex accordingly.

 

[Sleepydoc]

Look at your plumbing, but what you’re looking to do should be quite doable with one pump. The Varios-8 is a solid pump and could handle that flow. The current buzz is around the COR pumps that are being released; they look promising and should handle the flow you’re looking for. There are plenty of other options as well.

There are a couple of ways to approach the reliability goal you’re looking for. First, I would look at getting as reliable a pump as you can. Second, maintain it by cleaning it on a regular basis. Finally, you can prepare for a pump failure by either having redundant pumps, or having a backup pump. If you are away from your system for long periods of time, then a double pump might make more sense, but I prefer having a backup pump on hand. This also has the advantage of letting you swap them out to do maintance and/or being able to run the system normally if one should completly die. I actually have my backup pump in my mixing station. That way I’m making use of it but if I need to I can easily take it out if necessary.

 

[Newb73]

I am a big believer in running multiple pumps (I am running 2x varios 6s) but with a single return line you can do a few things.

1) install a flow meter w an alarm.
2) Program wave makers to switch to high if main pump goes off....and then immediately send you a message.
3) Just simply make sure your sump and water levels are set so the sump doesn't ever flood when main is out.

That said a y connector would be fairly simple i would think.

I also have a transfer pump in my sump plumbed to an external drain and a high level float switch that will lower the water in my sump automatically if the water line gets too high in sump....and one in my overflow that will cut my returns to 30% if water in display gets too in the display...lastly a self priming sunk pump will clear any water standing inside my stand above 1 inch as my stand is water proof and 5 inches deep. Leak detectors can tell if water is inside stand or on floor and will cut pumps of stuff that could be leaking or short out accordingly.

If you are going to be out of town for a few days, i find it prudent to just not run things like external skimmers, UV reactors, external reactors, automatic water change system etc....its either self contained in the sump...or it gets a vacation while im gone.

Exceptions are sulfur denitrators, 2 part dosers and pellet reactors of course.

 

[Reefrodeo]

As a civil engineer, and having read everyone’s response, I’d like to offer my two cents. First, some clarification:
1) If you run multiple pumps in parallel (through a wye or manifold) they will match head pressure on the pump curve and flow rate will be additive. If you want to run both pumps at once efficiently, the return line will have to upsized (possibly significantly) to account for added friction loss.
2) if you run pumps in series (in-line) they match flow rates, and pressure is additive along the curve. Overall flow will not increase as much, but discharge pressure increases.

Since you are looking at more of a backup system, parallel connection is what you want. I see two concerns with running dual pumps all the time: 1) check valves are required to prevent backflow in the event one pump fails, and IMO, should not be relied upon in a saltwater system, even with maintenance when kept in one position, and 2) running two pumps full-time increases power consumption and maintenance requirements.

If you are set on running dual pumps, it will be important for you to turn them off (feed mode) to allow check valves to operate, or ideally you could set up a routine through a controller to alternate pump operation to keep both in operating condition and cycle check valves, with a safety routine to switch pumps and alarm in the event of failure. But I’m not a programmer, and that may be beyond the limits of aquarium controllers.

Unless your tank is completely unattended for long periods of time, I personally think a better option would be to have a second pump on hand (out of tank) that can be quickly interchanged song with reliable controller alarm(s) to notify you of pump failure. A decent sized tank should be able to withstand a few hours with power heads only.

 

[Newb73]

If you are set on running dual pumps, it will be important for you to turn them off (feed mode) to allow check valves to operate, or ideally you could set up a routine through a controller to alternate pump operation to keep both in operating condition and cycle check valves, with a safety routine to switch pumps and alarm in the event of failure. But I’m not a programmer, and that may be beyond the limits of aquarium controllers.

Not exactly.

With DC pumps you can just lower the power without shutting them off.

In fact at around 20% power they stall, meaning the pump is on but head pressure cancels out force, water stops moving ..it isn't flowing back to sump...thats how you do feed mode with a DC.

Running dual returns also solves many of the issues you mention.

I don't worry about "resting" my pumps as they spend a large portion of the day at 30% power as it is...the chances of both failing in the same week is very low.

I do use check valves (flaps) but only to reduce how high the sump gets when i am doin maintenance, my sump is more thsn capable of holding all the back flow if they fail. (They cant prolapse but they could get stuck open).

The chances of one failing without me noticing is pretty much neil as both lines have flow meters and alarms.

 

[Sleepydoc]

I dont' think you're considering this, but you should note that running two pumps in series would probably make the system less reliable - If the first pump in the series were to fail, the second would be attempting to draw water through the failed pump, possibility causing cavitation. If it were reversed, the remaining pump would be attempting to pump water through the failed pump. If the impeller on the failed pump was frozen you would end up with virtually no flow.

Dual returns would be best, but you would still end up with significant back siphoning though one side if one of the pumps should fail.

 

[Reefrodeo]

Not exactly.

With DC pumps you can just lower the power without shutting them off.

In fact at around 20% power they stall, meaning the pump is on but head pressure cancels out force, water stops moving ..it isn't flowing back to sump...thats how you do feed mode with a DC.

Running dual returns also solves many of the issues you mention.

I don't worry about "resting" my pumps as they spend a large portion of the day at 30% power as it is...the chances of both failing in the same week is very low.

I do use check valves (flaps) but only to reduce how high the sump gets when i am doin maintenance, my sump is more thsn capable of holding all the back flow if they fail. (They cant prolapse but they could get stuck open).

The chances of one failing without me noticing is pretty much neil as both lines have flow meters and alarms.

I was responding to the specific case mentioned in this thread - Cornerboy does not want to run two separate return lines due to his sump's location, but seems intent on running dual pumps. My basis for recommending pump cycling is not related to variable flow, but rather complete shutoff to operate the check valves to keep them from getting blocked by growth from lack of operation. Dropping the flow rate of a DC pump simply causes it to dead-head and does not necessarily close the valve. Your comment on sump capacity is an important one, as it is a better failsafe than relying on check valves. Sump capacity may not matter in the case of one pump failing in a dual pump system, though, as the problem is recycling pumped water through the failed pump, not necessarily backflow from the tank.

One comment I would like to make on this whole discussion is that it seems that many of these options discussed continue to add to the complexity of a solution to a rather simple problem when you step back and look at it.
Maybe it's time to revisit K.I.S.S. (Keep it simple, stupid), and evaluate your research sources - K.I.S.S. doesn't sell hardware.

I love my Apex controller for monitoring and alarms, but nothing replaces quality equipment, failsafe design (this does not mean more technology), and observation (see my original recommendation).

 

[Sleepydoc]

One comment I would like to make on this whole discussion is that it seems that many of these options discussed continue to add to the complexity of a solution to a rather simple problem when you step back and look at it.
Maybe it's time to revisit K.I.S.S. (Keep it simple, stupid), and evaluate your research sources - K.I.S.S. doesn't sell hardware.

I love my Apex controller for monitoring and alarms, but nothing replaces quality equipment, failsafe design (this does not mean more technology), and observation (see my original recommendation).

This. I just watched the BRS video on ultra low maintenance tanks and when they referred to dual return pumps, it was in an all-in-one system with separate return 'plumbing' for each pump. For the OP's setup, I think optimizing the plumbing and purchasing a larger return pump would be the best option. S/he should also ask if they need a larger pump or not. You need enough sump flow to run your equipment and maintain equilibrium with the DT, but if you just need more flow in the DT, a power head is a fine way to go.