Flow rate estimate?

[slythy]

I have a sicce sdc 6.0 that is plumbed with 3/4 soft line. It goes about a foot up to my uv, then over another 2 feet to a T and split to my 2 3/4” returns. Total height is right at 4 feet.
I have my pump at 50% but it seems like water is barely coming out. I would have thought with the head loss at 50% i would be around 500?

anyone able to give me a close estimate?
Thanks

 

[vetteguy53081]

May be a little strong.
Any video of tank with pumps running ?

 

[slythy]

May be a little strong.
Any video of tank with pumps running ?

I have 2 out puts and they are both about that fast. Pump is set to 50%. Im trying to target around 500ish gph for the flow through my sump

 

[DCR]

I think you will need 1" line and pretty much full speed to get 500 gph. Sterilizers can also create a lot of restriction if small barbed fittings are used. I would try increasing the pump speed to get more flow first

 

[vetteguy53081]

I have 2 out puts and they are both about that fast. Pump is set to 50%. Im trying to target around 500ish gph for the flow through my sump

You can actually increase flow a little and assure the lockline is under water (submersed)

 

[slythy]

I think you will need 1" line and pretty much full speed to get 500 gph. Sterilizers can also create a lot of restriction if small barbed fittings are used. I would try increasing the pump speed to get more flow first

I cant believe at a sdc 6.0 wont run at around 1000gph at full blast with only 4ft of head. Its an aqua uv 57w with 3/4 barbs

You can actually increase flow a little and assure the lockline is under water (submersed)

I just lifted it for the video. I can just do a gallon jug CC fill it up and figure out flow rate that way. Might turn it up a little bit.

 

[slythy]

I think you will need 1" line and pretty much full speed to get 500 gph. Sterilizers can also create a lot of restriction if small barbed fittings are used. I would try increasing the pump speed to get more flow first

Man.... you were way right... I timed filling up a milk jug....

50% speed ~271gph
75% speed ~334GPH
100% speed ~369gph

Im shocked at the lack of flow out of the pump... at 50% its still 4x the tank volume through the sump... and it massively increases the dwell time through my UV lol.

Think I should shoot for 50% or step to 75%? 50% is a dead silent tank lol

 

[DCR]

If you are at 4X turnover, I would probably live with it and make sure you have powerheads in the tank for strong turnover. Your main problem is the 3/4" line between the pump and the tee. If you could upgrade that to 1", I think you might get to your 500 gph target. I design hydraulic systems as an engineer and I would generally not use a 3/4" line to carry more than 300-400 gph any distance. Your numbers are in line with what I would expect. Most people on this site overestimate their return flows because they assume the frictional head losses are minimal.

The problem is not the pump as much as your return piping size.

 

[slythy]

If you are at 4X turnover, I would probably live with it and make sure you have powerheads in the tank for strong turnover. Your main problem is the 3/4" line between the pump and the tee. If you could upgrade that to 1", I think you might get to your 500 gph target. I design hydraulic systems as an engineer and I would generally not use a 3/4" line to carry more than 300-400 gph any distance. Your numbers are in line with what I would expect. Most people on this site overestimate their return flows because they assume the frictional head losses are minimal.

The problem is not the pump as much as your return piping size.

yea i just wouldnt have thought that it would be so high. Clearly needed to study more in my fluids classes lol.

I have 2 mp40’s on my 70g so i have plenty of flow elsewhere. I could. Go 1” to the t instead of the 3/4 but i’m fine with how it is now too :/

 

[slythy]

@DCR

So I changed out my 3/4 line to a 1" line and then my 3/4 T into a 1" - 3/4 Y fitting.

50% = 332gph
60% = 390gph
75% = 408gph
100% = 510gph

so quite a flow increase. I am going to keep it at 60% as thats the best flow/noise radio. Gets me up to ~5.5x flow

 

[DCR]

I think you should be OK with those flows, but if you do decide to get a pump that will give you more flow in the future, I would look at one that delivers more head at the flow that you are looking for rather than the zero head rated flow. According to the Sicce head curve (100% speed), your pump should be delivering about 7 ft of head at 590 gpm which means you have 3 ft of head loss due to friction (assuming 4 ft of elevation gain). Fictional losses go up with the square of the flow so if you wanted 25% more flow with your current system you would have 3 ft times 1.25 squared or 4.7 ft of frictional loss plus the 4 ft of elevation gain or 8.7 ft at the 25% more flow over 590 gpm. I say all this to point out how fast frictional losses become prohibitive with increasing flow. This is why I say that expecting most low head pumps (20 ft or less at zero flow) to do more than 600-800 gph with 1" piping or 300-400 gph with 3/4" pipe is not realistic. This is all at 100% speed as well.

 

[slythy]

I think you should be OK with those flows, but if you do decide to get a pump that will give you more flow in the future, I would look at one that delivers more head at the flow that you are looking for rather than the zero head rated flow. According to the Sicce head curve (100% speed), your pump should be delivering about 7 ft of head at 590 gpm which means you have 3 ft of head loss due to friction (assuming 4 ft of elevation gain). Fictional losses go up with the square of the flow so if you wanted 25% more flow with your current system you would have 3 ft times 1.25 squared or 4.7 ft of frictional loss plus the 4 ft of elevation gain or 8.7 ft at the 25% more flow over 590 gpm. I say all this to point out how fast frictional losses become prohibitive with increasing flow. This is why I say that expecting most low head pumps (20 ft or less at zero flow) to do more than 600-800 gph with 1" piping or 300-400 gph with 3/4" pipe is not realistic. This is all at 100% speed as well.

Yea thats pretty insightful. The pump is brand new and I was fairly happy with my Sicce 9.0 on my 180g but again its pretty low flow. I probably should have gotten a slightly larger pump than the 6.0 but oh well. I do like the fact its controllable via my apex and you dont need any tools to disassemble it to clean. I think Im giong to be over flow'ed with my 2 mp40's anyway.