Combining 2 pumps

[vertigo72]

I want to add a second pump to my bio filter. Rather than hooking it up at the filter (requiring extra tubing and another tube coming over the edge, is there any reason this would be a bad idea:

Simply add a T under water and connect the new pump to the existing tube?
The tube is wide enough to handle the flow of both pumps.
Now I wonder if it will cause the pumps to "fight" or not. You would think so, but then if I put that T right at my filter, it would have the exact same result, or not? Im confused lol.

 

[DrCase]

You need the hose off the pump , To be the maximum size of the pump outlet to get the best flow it could put out.
You would need to double that adding the second pump

 

[vertigo72]

Im not sure I understand what you are saying, but the more I think about it, the more it seems like a bad idea, regardless of the diameter of the hose (which is wide enough). Ill just get another hose and make something at the filter so I can connect it without the second pump having to fight with the pressure of the first.

 

[fishin4cars]

Vertigo, What he is trying to say is if each pump has a 1" outlet coming from the pump, then where you connect the two lines together it would need to go up to at least a 2", If they are 1 1/2" outlets at the pump you would need 3" where the two come together.

 

[vertigo72]

Not to nit pick, but if thats what he meant, he is actually incorrect. A 1.5" tube has ~2x the throughput of 1" tube, and a 2" has ~4x the throughput of a 1". So even if I was "tube limited", I certainly wouldnt have to double the size.

Anyway, the real problem here is pressure, and thats why its a stupid idea. I have to tube the second pump to the filter and connect in such a way that the only pressure the second pump has to overcome is the height to the filter, rather than height + perhaps 1/2 the pressure from first pump.

 

[Malak]

Why not have two inputs i.e. totally separate lines that never the twain(sorry Shania) shall meet?

 

[vertigo72]

Why not have two inputs i.e. totally separate lines that never the twain(sorry Shania) shall meet?

I wanted to avoid that, since its an old concrete pond, so you can see the tubes and they have to go over the edge. That, and to save money .

 

[mogsie]

vertigo72, can you please explain to me how a 2" pipe has 4 times the throughput of a 1" pipe ? ime a little confused thanks,

 

[vertigo72]

A 1" circle has 3 square inch surface area. A 2" circle has a surface area of 12.5 square inch. Throughput isnt the right word though, as pressure and velocity factor in, but roughly you can pump 4x more water through a 2 inch pipe compared to a 1", at a given pressure and speed.

 

[mogsie]

yes of course i understand you now, thanks

 

[ginger_biscuit69]

be sure that the filter can handle the extra water flow as well.

Rule of thumb, gravity returns need to be twice the size of a pumped inlet (1" pump in, 2" gravity out), although adding an extra inch is always advicable. 3" gravity return is good for about 10000L/hr with some extra 'emergency' capacity.

 

[vertigo72]

Indeed. Fortunately I do have 4.3 inch (110mm) return and intra-barrel pipes (is that a word lol?), as I planned on this from the start. I just hooked up the second pump (on its own inlet) and as I expected, its borderline with a 15000 L/h + 8000 L/h pump both at ~2 meter head. Water rises more than an inch above the return pipes, and I was stupid enough to position the bulkheads quite high, so water is now only an inch from the edge in my first barrel. Its probably also too much flow to have much benefit from the vortex, so Ill probably put a T on one of the pumps and use some of its capacity to circulate water around in the pond, possibly with a venturi.

 

[ginger_biscuit69]

was there a need for the increased flow?

stalked your profile, see it's about 50,000l concrete in a bowl type of formation. Assume the bigger pump is in that central recess and the rest of the pond is leaning down towards this point.

Assuming the filtration is coping physically with the 15000l/hr pump, id use the 8000L placed with the output firing straight out the unit, to make a pond current spinning around, turning the entire pond into a vortex with the large central pump taking out this waste to the vortex then filtration?

 

[Malak]

that's clever

 

[vertigo72]

was there a need for the increased flow?

stalked your profile, see it's about 50,000l concrete in a bowl type of formation. Assume the bigger pump is in that central recess and the rest of the pond is leaning down towards this point.

All correct. Do I need more filtration? Biologically/chemically, no. My fish load is extremely light for such a large pond, I have absolutely no ammonia or nitrites problem. I probably wouldnt have one without the 15K pump and DIY filter, as there is also a fairly large iris bed (although its in clay and water is merely running over it, not through it. Very poor design, but it is what it is. Its fed by a third pump btw, not sure about the capacity, but I estimate around 5-6000L/hour).

Some Koi have grown huge and survived for decades in this pond with just those irises and that pump. I added all the rest recently, as, well, those koi didnt survive in the end (mass die off from parasites a few years ago) and the entire pond had become a giant mud pool.

Mechanically, I need everything I can get to have any hopes of keeping the water somewhat clear. The pond is surrounded by overhanging trees and bushes, and there is a slope. The amount of stuff falling in is absurd and not all of it floats. But much does, so I really need a skimmer. Ideally Id need many skimmers in fact, but if youve seen pics of the pond, you may understand its not easy to install.

As to this:

Assuming the filtration is coping physically with the 15000l/hr pump, id use the 8000L placed with the output firing straight out the unit, to make a pond current spinning around, turning the entire pond into a vortex with the large central pump taking out this waste to the vortex then filtration?

Thats pretty much what I was thinking, and why I said Id add a T and use part of one pumps capacity for just that purpose (perhaps with an added venturi, although I already have a large airpump with a disc in the pond and several stones in the filter).

A few problems with that though:
1) my waterlilies dont like this idea
2) I already tried it for a while, and the pond is not uniform enough to create a real vortex. The pond is formed like a croissant and the resulting flow is complex. Pumping water around does help, but not like it would in a round pond.
3) im gonna need some pumping capacity for a makeshift "skimming lava filter" that I intend to make in one of the "croissant tips". See here:
https://www.gardenpondforum.com/lava-filter-t7926.html

Now believe it or not, I still have a 4th pump laying around, its a "basement pump". Its extremely powerful, 25K liter per hour or so, but its also a power hog (1000W). So I think Ill use that pump for the vortex, but put it on only a few quarters of an hour per day on a time clock. Then use the 8000L pump for the lava bed/skimmer I have yet to make, and I might as well feed that back to my biofilter. Not sure about that yet.

Anyway, I appreciate your thoughts.