Rdwc Pump Sizing

[peta1111]

I am currently putting together a system using (2) 8-gallon buckets + 20-gallon res. I've decided to push water into the buckets (waterfall) via a pump from the res and allow the water to return via 2" pvc. I'm planning on using either 1" or 3/4" feed lines. I'd like to use the same pump to drain the system by installing a ball valve to a drain line. In looking at pumps there is not much difference in price from 550gph to 1000gph pumps -looking at the Active Aqua pumps on Amazon.
I'm wondering if the bigger pumps may end up having too much force though. It seems that those pumps are only adjustable if used in submerged mode and I was planning on using it inline. Also, if I go with a larger pump and use a ball valve to adjust flow rate to the pump will that hurt the pump?
Any recommendations and advice appreciated.

 

[agent dank]

I think the only thing that will happen is the water will come out faster by throttling a pump. Which is probably ideal for a waterfall as you want as much surface disturbance as possible.

Although youre just adding more friction (heat) in your water so id get a properly sized pump.

I have a 1000 for a 140gal rdwc. Think thats overkill for your 36gal setup.

Also the more oversized your pump,is you run the risk of cavitation when air pockets form on the pump impeller and implode basically. Damages impellers.

 

[peta1111]

I think the only thing that will happen is the water will come out faster by throttling a pump. Which is probably ideal for a waterfall as you want as much surface disturbance as possible.

Although youre just adding more friction (heat) in your water so id get a properly sized pump.

I have a 1000 for a 140gal rdwc. Think thats overkill for your 36gal setup.

Also the more oversized your pump,is you run the risk of cavitation when air pockets form on the pump impeller and implode basically. Damages impellers.

Thanks. For the extra $20-30 I decided to use separate pumps to feed the system and to drain system - since I need to go up roughly 7' to drain.

 

[agent dank]

0.433 PSI per vertical foot of elevation rise.

What i did was hook up the pump so it pumps into the chiller but before it goes to the chiller is a tee that has a ball valve and a barbed nipple for use with polyethylene pipe. Thats my drain.

On the supply from the chiller to buckets. I close that valve to divert flow to the tee which has rhe ball valve thats normally closed, open to drain.

 

[peta1111]

0.433 PSI per vertical foot of elevation rise.

What i did was hook up the pump so it pumps into the chiller but before it goes to the chiller is a tee that has a ball valve and a barbed nipple for use with polyethylene pipe. Thats my drain.

On the supply from the chiller to buckets. I close that valve to divert flow to the tee which has rhe ball valve thats normally closed, open to drain.

I was planning on doing something similar with ball valves but the pump to drain is going to need to be more powerful to get to the height and distant I need it so I may as well use 2 different pumps. But I am going to try the larger pump on the system first just to see

0.433 PSI per vertical foot of elevation rise.

What i did was hook up the pump so it pumps into the chiller but before it goes to the chiller is a tee that has a ball valve and a barbed nipple for use with polyethylene pipe. Thats my drain.

On the supply from the chiller to buckets. I close that valve to divert flow to the tee which has rhe ball valve thats normally closed, open to drain.

After I read your posts last night I was thinking about the pump some more. I have a 1000g active aqua pump that I was planning on using to drain the system. The 1000g pump has a restrictor at the input end to provide flow control. If you use the pump inline instead of submerged though that piece comes off. So I took a look at it. The flow control knob only restricts the amount of water that flows into the pump. The same can be accomplished via the ball valve that sits just before the pump in the inline layout. That ball valve is necessary anyhow in case the pump needs to be removed from the system for cleaning,service, or replacement. So I think I am going to try putting the 1000g pump in the system, inline with the ball valve and union, and try to set the flow using the ball valve. If I'm not happy with it then I will buy a smaller water pump that can be directly substituted into the configuration and I'll use the 1000g pump only for drain. The smaller pumps are only $20-$30. I have to setup the system to test run it anyhow. So we will see soon enough. I hope to complete everything in the next week.

 

[agent dank]

You dont ever wanna throttle the pump on the suction side. This causes cavitation. You also dont want long suction lines, too small of pipe for suction line or too many bends/fittings.

 

[agent dank]

Also 7 ft is pretty high for these kinds of pumps.

They are rated for 4.9PSI. Just getting the water vertical 7ft youre losing 3.031PSI

But the 550 is only rated for 3.5PSI. Depending on how many feet of linear and fittings,my,guess is the 550,wont give the lift you need.

 

[peta1111]

The manufacturer shows the head (FT) in height graphs for all of the pumps. The 1000 gets me the 7' at roughly 700gph. The 550 is not enough. Also to be clear the 7' is on the output side of the pump and only used for draining the system (occasional use). My suction line is short, maybe a foot.

I do not doubt you but why would the manufacturer provide a built in input throttle and even state in the instructions that it is for throttling the output flow if it is detrimental to the pump?
I'm still going to try it to get a feel for the flow.

Also, there will be some throttling on the output which should help match the input

 

[PhatNuggz]

You can significantly simplify your set up by connecting the pump to the lower drain line. Even my hydro store did not know that the pup tube can also act as the drain-back. See my Hail Hydro thread