Calling all plumbers and pump experts

[peterac]

I have a tank with 2 Dolphin Aqua Sea 2100's returning water from my sump. The flow rate seems to be way too low for what these pumps are rated at. I was wondering if the way I have these configured is causing this slow down.

Each pump has a 2" outlet that splits right off the outlet into 2 separate 1" returns. Each 1" run on one of the pumps goes for about 5' horizontally with 2' of head. Each 1" run on the other pump goes for a tille less horizontal with the same head. Just before they attach to the bottom of my overflow box at a bulkhead, they go through a check valve and are further reduced to 3/4". The 3/4" run goes vertically up the overflow box where it splits into 2 outflow ports. So there are a total of 8 outflow ports.

Maybe because the overall flow is spread out over 8 ports it feels very weak to me? I did a very rough estimate by shutting off the pumps when I truned them on I calculated the rate in my sump to remove a given volume. My very rough estimate for the overall circulation is about 900 gph, which is only 2X for my tank. Even if I was off by several hundred gallons as an estimate, it is still not close to the specs of 4200 gph combined.

I think the way this tank was designed with the 3/4" returns from the bottom of the overflow box to the outlet ports requires that I get pumps with smaller outlets (3/4" or 1").

Everyone's thought are graciously welcomed as always.

Regards,
Pete R.

 

[fishfreek]

You may be better off running 2" PVC from the pump to just below the overflows and then break that down to 2X 1" and then down to 3/4". Their is a limit to how much water can flow thru a specific diamater pipe and you are probably adding alot of 'virtual' head by having the smaller diamater plumbing. I dont work with fluid dynamics at all but I honestly thing you can get more thru 1 2" pipe than 2 1" pipes. Also if you split the 1" out to two 3/4" lines you might be better off.

This is how I measure flow rate thru a sump system. Since its very hard to measure the pump output given the multiple outlets see if you can measure the overflow's rate of flow. Since in theory the main tank is at a stable water level until the sump's pumps begin putting water into the tank. The only water comming out of the overflow is due to the water going into the tank via the sump pumps. So the water comming out of the overflows should roughtly equil the amount of water going into the tank via the sump.

 

[mp3z24]

time for me to be an engineering nerd... yes i have taken fluid dynamics, it is basically what i do every day... :?

flow area is the key parameter for minimizing pressure drop in piping. if you consider the area of a 2"pipe, it is 4 times the area of a 1" pipe. so when you split your 2" pipe down to two 1" pipes, you have effectively reduced your flow area in half. so, the pump will "see" a lot more resistance to flow, and it will make the pump run at a less than optimal point. pumps will increase or decrease the flowrate out to match the pressure drop. so, high pressure drop means low flow, and low pressure drop means high flow. this is how it is for all pumps...

also, something to keep in mind, when pump manufacturers rate their pumps, they will usually rate them in maximum flow. that is, the flowrate of water when there is NO resistance in the system. that means the only way you will see that "rated flow" is if there are no pipes on the inlet and no pipes on the outlet, basically like a re-circulation PH on the back wall of a tank...

so, if you really want to split that pipe immediately after the pumps, then i would tell you to use 1.5" piping. also, try to minimize the number of fittings in the system. all they do is add pressure drop.

~mike

 

[fishfreek]

Excellent.

 

[loganj]

I'd probably ditch the check valves too. You can get a manifold fitting for these pumps that splits right off the pump into 6-8 3/4" lines. The plumbing involved in getting from that to the tank would probably terrify even a veteran plumber, but you'd have some nice currents in the tank. Also, if I remember correctly (yeah, right 8O ), these pumps are not pressure rated so they won't deal with flow restrictions well.

 

[peterac]

Thanks for the feedback. I may just go for pressure rated pumps since these Dolphins are a few years old. I saw some Iwaki models that had 1" outlets so I would not be reducing until just under my overflows. Thanks....

While on the topic of fluid dynamics....I have been perplexed with the following:
When a sump is all setup correctly there is a fluid level that is reached when the return pumps are running. How is this level achieved? In other words, in my mind I am thinking that if the overflow rate is larger than the pump's return rate then the sump will eventually overflow and on the contrary, if the pumps are returning water at a faster rate than the overflow then the sump level will eventually drop to the pumps outlet openings. I am probably not making too much sense - the basic question is why is the level in the sump constant without making adjustments to the pump rate?

Thanks,
Pete R.

 

[loganj]

Because the overflow can only return what the pump puts in the tank. It doesn't matter what the flow rating of the overflow is (unless you exceed it of course). Once you reach the level in the main tank where water is spilling over the wall of the overflow, the water that spills over, and only the water that spills over, will be returned to the sump. If you exceed the flow capacity of the overflow, the most likely outcome is that the main tank will overflow into the floor. HTH.

 

[ellisz]

Any good references or sites on building manifolds? I am planning a basement sump with a big return pump(Panworld 200PS) and will have it supply my refuge and maybe a prop tank later on.

Thanks

 

[loganj]

I can get two different ones. One is a spider manifold that goes from 1.5" to eight 3/4 hose barb outlets. The other is a straight manifold that goes from 1.5" to six 1/2 slip ports. The first one has the outlets perpendicular to the inlet. The second one has the outlets parallel to the inlet. These are for Dolphin pumps and are the only ones I've ever seen. You could build one using PVC crosses or double Y fittings. I'm not sure how well it would flow though...the Y fittings would offer less resistance. They are typically drain fittings though so I'm not sure if you can get them in the sizes you'll need. Did you know that the Panworld 200PS is the same pump as the Blueline 70HD? Funny how you can get the exact same product under different brand names.

 

[ellisz]

I wish one of them was cheaper I was told the flow was the same as the Iwaki 70RT. Is this correct? I want it to feed my tank 15-16ft up from the basement and supply my fuge and later a prop tank. I think I can get the fuge in the 100 gal rubbermaid stock tank I bought for my sump. If I set up the fuge in the sump, I guess it can get its flow from the tank drain. Then all I would need is to supply the prop tank.

A quick way to do water changes would be nice too

 

[loganj]

The Iwaki 70RLT is rated at 1536gph @0' head with a shut off head of 32'. The Blueline/Panworld pump is rated at 1750gph @ 0' head and has a shut off head of 39'. Unfortunately, the price is about the same for either one. If you had a valved tee in the pressure line coming from the pump running to a drain, you could easily pump out water from the sump to the drain. Then, if your SW mixing container was sitting close to the sump, you could pump new SW into the sump. It would be pretty easy to set up.