Question about calculating head pressure

[CindyKz]

I currently have a 180 gal DT, 100 gal sump, 30 gal frag tank and 20 gal refugium plumbed together in my basement. Turnover in the DT is roughly 1100 gph.

I want to plumb in a 75 gal tank upstairs. This will require about 20' of vertical pressure that I don't currently have. Desired turnover in the upstairs, 75 gal tank will be low, roughly 250 gph.

When using online head pressure calculators, do I use the desired flow in the upstairs tank (250 gph) or the downstairs tank (1100 gph)? The larger tank is downstairs so minimal vertical head.

I've tried it both ways and it makes a significant difference in which return pump I have to buy.

TIA.

 

[rwreef]

Calculate for the tank with the most head pressure. In your case the upstairs tank. Then understand the impact on the low head pressure system

 

[CindyKz]

Then understand the impact on the low head pressure system

Not sure exactly what this part means. If I understood it, I wouldn't be asking.

 

[GlassMunky]

Not sure exactly what this part means. If I understood it, I wouldn't be asking.

If you have a single pump as the return for both tanks, the leftover flow from the pump that isn’t directed into the 75g tank will be directed to your 180, so you kind of have to balance the flow to both

 

[CindyKz]

If you have a single pump as the return for both tanks, the leftover flow from the pump that isn’t directed into the 75g tank will be directed to your 180, so you kind of have to balance the flow to both

Thank you, that makes sense.

So if I understand you both correctly, I could use a pump that delivers appropriate flow to the upstairs tank, as long as there is enough left over for all of the downstairs tanks?

ETA. ugh. In other words, calculate based on the vertical head on the upstairs tank.

 

[GlassMunky]

Thank you, that makes sense.

So if I understand you both correctly, I could use a pump that delivers appropriate flow to the upstairs tank, as long as there is enough left over for all of the downstairs tanks?

ETA. ugh. In other words, calculate based on the vertical head on the upstairs tank.

Correct

 

[Cwentz758]

Might also be easier to get a second return pump dedicated for the 20’ head height for the new tank. Then later you can add things of that plumbing.

 

[ca1ore]

This is going to be tricky to calculate. I’ve found using a single pump for multiple systems with vastly different back pressure profiles to not work well. Can you use two pumps?

20’ is a lot. In order to get flow up that high, you’re going to need to significantly constrain the zero head output ..... effectively adding back pressure. My guess, and just a guess, is that you’re going to need something that nets around 750 at 20’. That is not a long list.

 

[CindyKz]

Might also be easier to get a second return pump dedicated for the 20’ head height for the new tank. Then later you can add things of that plumbing.

That is also an option, but I'd prefer one pump if possible.

 

[CindyKz]

So if I am doing this correctly, here is a list of pumps that might work in my "affordable" range. I can restrict flow to any tank with ball valves so I'm not worried about too much flow in any given tank.

The upstairs tank only needs about 350 gph.

Iwaki MD70 RLT
Dolphin AmpMaster 6250
Pan World 200PS (out of stock everywhere though)
Reeflo Hammerhead - not really a contender based on multiple reviews of leaking seals

 

[DCR]

You will need a pump that delivers the combined flow rate (1100 + 350 gph = 1450 GPH) at the 20 ft of head (study the performance curves). Then you will kill the head pressure to the lower tank by throttling down on the flow to it. I am not sure if all of those pumps can do that - at least not the Iwaki or Pan World). It is going to be a very large and powerful pump. You would be better off using different pump for the two different tanks due to the different head and flow requirements.

 

[CindyKz]

OK. My hubs did some measurements for me and I can't for the life of me figure out where some of these numbers came from. He was measuring while I wrote, and he was talking to me while I was trying to write, and all I can figure is that I transposed numbers while multi-tasking

Depending on whether I measure from the floor, the pump, or the water level in the sump I get a variable 8.5 to 11 feet of vertical. Which makes a lot more sense, we have a standard basement. No vaulted ceilings down there!

Back to figuring. I'm using 11.42 vertical feet - 80 inches floor to ceiling (the pump sits on a pad on the floor), 6" to generously get through the flooring, 30" for the stand (it's custom and short) and 21" for the tank itself.

 

[CindyKz]

20’ is a lot.

I'm glad you said this, because I was thinking the same all along. Your comment prompted me to go re-measure.

 

[CindyKz]

You will need a pump that delivers the combined flow rate (1100 + 350 gph = 1450 GPH) at the 20 ft of head (study the performance curves). Then you will kill the head pressure to the lower tank by throttling down on the flow to it. I am not sure if all of those pumps can do that - at least not the Iwaki or Pan World). It is going to be a very large and powerful pump. You would be better off using different pump for the two different tanks due to the different head and flow requirements.

I'm a little confused why I would need such high flow at the 20'? That's where the smaller, lower flow tank is. Just trying to understand, now that I've realized I don't need 20' after all.

 

[CindyKz]

I'm a little confused why I would need such high flow at the 20'? That's where the smaller, lower flow tank is. Just trying to understand, now that I've realized I don't need 20' after all.

Nevermind I think I get it. Calculating for total flow throughout the system?

 

[CindyKz]

I think I am going to reconsider a second pump. Life will be much easier.

 

[CindyKz]

OK, I gotta talk to hubs, because for some reason that I don't understand he really wanted to run everything off one pump. But running a second pump really does seem much simpler.

Right now I use a Fluval SP6. A second one dropped into the sump for the upstairs tank should work just fine, and would really simplify the plumbing as well (no cutting apart my established system or worrying about messing up the flow). Then all I'd need to buy is another backup so I have always have a spare.

Thanks to everyone for helping me think this though.

 

[jda]

Yes, go with two pumps. Get a PanWorld, Blueline or Iwaki and save yourself the trouble from the get-go.

If PanWorld 150 (Blueline 55) works, then don't go any higher since the wattages really start to jump after that. They are great pumps.

Some DC pumps advertise that they can do 12 feet of head, but they are often short lived and don't really perform as advertised. Even if they can handle that kind of head, they are usually run at 100% and take the same wattage as a PanWorld and do a worse job. Abyzz and Red Dragon are exceptions to this if you can afford them.

 

[JoshH]

6" to generously get through the flooring

Is this ceiling drywalled? Or open joists? If it's a drywalled ceiling in the basement you're probably looking at about 10-14" to get through the drywall and up to floor surface on the next level depending on how tall the floor joists are...

 

[CindyKz]

Yes, go with two pumps. Get a PanWorld, Blueline or Iwaki and save yourself the trouble from the get-go.

If PanWorld 150 (Blueline 55) works, then don't go any higher since the wattages really start to jump after that. They are great pumps.

Some DC pumps advertise that they can do 12 feet of head, but they are often short lived and don't really perform as advertised. Even if they can handle that kind of head, they are usually run at 100% and take the same wattage as a PanWorld and do a worse job. Abyzz and Red Dragon are exceptions to this if you can afford them.

Thank you for the input! I haven't really considered a DC pump anyway. I don't really get the attraction, I'm more of a "set it and forget it" kind of person.

If I use a second pump it will need to be internal, which is ok. Lots of options. The benefit of using another Fluval is that I can interchange them if I need to.