From 3” to 2” pipe leading to pump?

[RadarContact1]

I’m planning on transitioning from an internal pump to an external pump. Where I’ll be coming through the liner with a bulkhead is about 90° from where I want the water to come from. In other words, the bulkhead will be on the north side and the water will enter the pipe on the west.
So that means I need to turn the pipe once it enters the pond and run it around the bottom until it gets to where I want it to dry water from. I was going to use an elbow right after the bulkhead, but I know that will restrict flow and I’m already pushing the limits of a 2 inch pipe. So I was wondering if there is anything wrong with using 3 inch pipe from inside the pond, A 3 inch elbow to the bulkhead, a 3 inch bulkhead, a 3 inch elbow on the other side of the bulkhead, and then transitioning down to 2 inch pipe for my main run to my pump then filter.

I don’t think I was able to explain that very well so please ask questions so that you can help me!

 

[RadarContact1]

P.s.
Pump sits above the water line by about 6”. I’m looking at self-priming pumps only.

 

[zeuspaul]

Friction losses are cumulative. You would add the losses in the 3" pipe to the losses in the 2" pipe. The total loss will be less with the inclusion of 3" pipe.

 

[RadarContact1]

I’m really not sure what that means.

I think you’re saying that the 3” pipe wouldn’t be a problem and will also be less restrictive than if I were to use all 2” pipe?

 

[zeuspaul]

That's right. No problem using 3" pipe and yes it will be less restrictive than all 2" pipe.

 

[addy1]

Welcome to our group!

I draw from a 3 inch pipe in the pond and reduce to a two inch pipe right near the pump. Have a few joints and a angle. My pump is external. It works just fine.

I draw around a foot off the bottom of the pond, but my water goes right into my bog so I do not want to pull a lot debris from the pond bottom. IE snails, plants etc. The bottom of my pond stays pretty clean by itself.

I put a 5 gallon bucket with a lot of holes drilled in it around the intake, keeps the draw down so I don't suck in fry or other things.

 

[RadarContact1]

great, thanks guys!

As for the intake, I was going to go simple, using one of these grates at the end (attached).
My goldfish are very large, and I’m trying to get rid of the snails and tiny fish (that I regrettably introduced years ago) when I do the renovation. I think this might be alright.

 

[mgmine]

I push water 50 feet using a 2" pipe all the way. It goes up a hill 15 feet and is pushed into a 275-gallon tank. I have no problem at all and have to use valves to keep the water from overtaking the capacity of the tank. As I pointed out in your other thread water is better pushed than pulled. In a set up this small and a pump as powerful as you are thinking about friction will not be an issue no matter how many bends you puty in it. Just the opposit you will havbe to slow the pump down.

 

[RadarContact1]

Hmmm..

I push water 50 feet using a 2" pipe all the way. It goes up a hill 15 feet and is pushed into a 275-gallon tank. I have no problem at all and have to use valves to keep the water from overtaking the capacity of the tank. As I pointed out in your other thread water is better pushed than pulled. In a set up this small and a pump as powerful as you are thinking about friction will not be an issue no matter how many bends you puty in it. Just the opposit you will havbe to slow the pump down.

Funny you should say that, because I’ve been contemplating going full 3” pipe now. It will provide more water, whether needed or not, but will also reduce the pressure to a more manageable level (based on simple calculations).

 

[addy1]

I push water up a 40 ft more or less hill, with a separate pump then my main pump. My main pump only could push around 5 feet up the slope. The small pump is rated to handle 125 feet of head pressure. We run it on a timer.

 

[Ronfire]

If you can stay with 3" for as far to the pump as possible would be best for better flow with less friction loss.

 

[GBBUDD]

a 90 degree elbow weather 2" 3" or 4" matters little they are all restricting flow as the water comes down the pipe and finds a wall in front of it that diverts the flow in the direction of the opening never use 90's if at all possible if you must do to tight spaces a STREET 90 is at least a swooping elbow. But your are far better off with 4- 22.5 elbows or 2 -45 degree elbows To recommend you jump to a 3 inch line without knowing the pump volume and its head loss can't be done intelegently