Plumbing question

[kc]

Currently my sump has 3 holes and each connects to a Iwaki MK4 pumps which is a 3/4" inlet and outlet. Now I want to purchase a sequence dart to replace 2 of the MK4 pumps, but not sure should I redrill the sump with a 2" hole or use some plumbiing adapters and flexible pipe to connect to the sequence. I can't use any hard pvc because the sequence inlet will be higher
than the bulkhead.

Thanks
KC

 

[Meche]

What is the inlet size on the new pump?

 

[kc]

the sequence dart is 2" for the inlet and 1 1/2" for the outlet

 

[Meche]

You do not want to suck through (2) 3/4" straws for the 2" inlet.

A 2" inlet requires about (8) 3/4" tubes, or (4) 1", or (2) 1.5", or just one 2".

I would suggest plugging the two holes and drilling for (2) 1.5" pipe.

 

[Krish]

I agree with Brett on the 3/4 holes. The pump will probably overheat trying to suck with such restriction...

 

[kc]

I will drill a hole for the new pump. For the 1 1/2" outlet, I will connect to a Y connector and then feed it to the existing 2 3/4" pipe, do you think that will work? Currently, a MK4 pump connect to a 3/4" seawirl and one connect to a spray bar. Do you think this upgrade will change the flow in the tank?

 

[szidls]

Hey KC,
The Dart is rated 3600gph @4' head. My first question is what is your overflow capacity? Are you going to use the dart for your return pump? It sounds like you should use the dart as a closed loop pump and one of your other pumps as a return.
Scott

 

[Meche]

Szidls makes an excellent point.

Regardless of your answer to his question, it would not be a good idea to reduce the outlet of the pump either.

What is important is the cross-sectional area of the pipe, not the diameter.
So the area of a 1.5" circle is (area=Pi*r*r) 1.77sq in. The area of (2) .75" circles is only .88sq in.

You would actually need (4) 3/4" pipes to flow your pumps output as efficiently as (1) 1 1/2" pipe.

I know that sounds a little wierd but it's true.

 

[kc]

It sounds like I need to buy more power heads to increase the flow in my tank instead of getting a larger external pump.

Thanks for all your help.
KC

 

[Meche]

It sounds like I need to buy more power heads to increase the flow in my tank instead of getting a larger external pump.

What about a closed loop? Just connect the large pump to a network of pipes that come from and go to your tank.

It is a much cleaner look than a bunch of powerheads.

 

[Krish]

Regardless of your answer to his question, it would not be a good idea to reduce the outlet of the pump either.

Hey Brett...What's wrong with reducing an output from a pump? People do it all the time to create more pressure in the tank. You don't ever want to restrict the input I agree, but the output is done everyday when more pressure is needed in the tank

 

[Meche]

What's wrong with reducing an output from a pump?

It can be done. It won't make the pump cavitaite, like restricting the input will, but it will put a severe restriction on the outlet side. It will be like putting a bunch of elbows on the output. Just reduces flow too much.

If he has to do it, fine. But why not just go with a smaller pump that costs much less?

People do it all the time to create more pressure in the tank.

I dunno man, doesn't make sense to me. Reducing the area of the plumbing going into the tank will only increase velocity and reduce pressure. Just like a venturi.

 

[Krish]

Think about a penductor or better yet a garden hose. You turn on the hose and the water pours out. You put your finger over the output of that same hose to make the openeing smaller and what happens? You can shoot water 5 times the distance with more pressure

 

[Meche]

You can shoot water 5 times the distance with more pressure

You have your physics backwards Krish. I know it is hard to imagine, and counter intuitive, but what is actually happening is like I said.

The velocity goes up. Which is why it goes farther. Pressure actually drops to zero in a free-jet, like you describe.

 

[Krish]

LOL! Never took physics past primary school but I guess we tend to think of more pressure as more flow

 

[Meche]

but I guess we tend to think of more pressure as more flow

It only makes sense when you look at the math. I actually questioned my professor so much durring that class that he told me to stay after class. When class was over, he tought me the next chapter and showed me with the bernulli/ energy equation. Once I made sense of it, I was like, "ooooohhhhhhhh"

:lol:

 

[Scooterman]

The Dart isn't designed to be used as a pressure rated pump, returns tend to have lots of head to deal with. The Dart has a 2" inlet suction but can run just as well with a 1 1/2" inlet just a reduced output according to the manufacturer, also you can use a gate or ball valve to reduce the output if necessary, this will reduce power consumed also, these characteristics are typical for the centrifugal pumps.
On the garden hose think I think Krish is meaning that is you pinch the output off you will see whatever pressure that is being supplied like if it was completely closed & if you let it squeak out then yes it will drop off until if it completely free flowing. Once the water passes though the restriction basically pressure isn't a concern, I think that is said correctly?