Sump Returns

[LbulletM]

So, what is the guidance on the return section of a sump? I notice that they are mostly larger than needed for the actual pump itself.

 

[Crabs McJones]

So, what is the guidance on the return section of a sump? I notice that they are mostly larger than needed for the actual pump itself.

Are you making a sump and inquiring about how big to make the return section chamber? I'm not sure I understand the question

 

[redfishbluefish]

For my sump, the return section has to be large enough to take the back-flow of water when the pumps are turned off. When I designed by sump, I calculated the back-flow volumes and that helped in the size of this section, and the location of the ATO float switches. Here's my sump, with the return section in the middle, and shared with the biopellet reactor.

 

[LbulletM]

Are you making a sump and inquiring about how big to make the return section chamber? I'm not sure I understand the question

Well, yes and yes/no. Just wondering why they have to be so big instead of just large enough to house the pump itself. Trying to maximize fuge area.

For my sump, the return section has to be large enough to take the back-flow of water when the pumps are turned off. When I designed by sump, I calculated the back-flow volumes and that helped in the size of this section, and the location of the ATO float switches. Here's my sump, with the return section in the middle, and shared with the biopellet reactor.

Ahhhh, so it's to accommodate back-flow without flooding the entire sump in cases of normal on/off operation?

 

[Porpoise Hork]

Well, yes and yes/no. Just wondering why they have to be so big instead of just large enough to house the pump itself. Trying to maximize fuge area.


Ahhhh, so it's to accommodate back-flow without flooding the entire sump in cases of normal on/off operation?

The return side should be large enough to house the pump(s) and ample space for them to be completely submerged and any backflow should they shut off due to mechanical failure, power loss, maintenance, or feeding. Ideally you want a one way check-valve on the return side as well as a ball valve to prevent a siphon starting in the return line should one of the previously mentioned situations happens.

 

[LbulletM]

The return side should be large enough to house the pump(s) and ample space for them to be completely submerged and any backflow should they shut off due to mechanical failure, power loss, maintenance, or feeding. Ideally you want a one way check-valve on the return side as well as a ball valve to prevent a siphon starting in the return line should one of the previously mentioned situations happens.

So with a siphon break, really you only need adequate volume for what would be entrained in the return piping?

Also, how does a ball valve prevent siphoning? Or is that just for manually closing the line?

 

[ca1ore]

The size of the return section will dictate how frequently the ATO triggers. In the early days of reefing where the ATO was less common, a larger return section meant adding FW less often. Other than that, as long as the return section fits the equipment you need it to fit, smaller is better. In most sump designs, the volume of the return section won't have any relationship to back siphon - you have the entire sump volume for that.

 

[LbulletM]

The size of the return section will dictate how frequently the ATO triggers. In the early days of reefing where the ATO was less common, a larger return section meant adding FW less often. Other than that, as long as the return section fits the equipment to need it to fit, smaller is better. I don't really see how the size of the return section has any relationship to back siphon - you have the entire sump volume for that.

Fair take. Didn't think about the top-off implications. Have an ATO, so shouldn't be an issue.

I guess I was just inferring from above that it was better to have your return section take back flow rather than flooding the entire sump.

 

[ca1ore]

I guess I was just inferring from above that it was better to have your return section take back flow rather than flooding the entire sump.

It depends on how you design the sump. The one pictured above has all full water height sections other than the return, so there isn't anywhere for a whole lot of backflow to go beyond that one section. I wouldn't personally design a sump that way, though YMMV. Beyond that, as long as you have adequate backflow space, regardless of which compartment, you will be good. I would not personally rely on a check valve - been there, done that. They almost always fail.

 

[LbulletM]

Yea, I'm planning on just a simple 3 baffle sump - inlet/skimmer, refugium, return - left to right. Also going to do it in a 29g for a 29g display (this is a stop gap since my 150g upgrade is delayed due to probably moving in the next year or two), so I should have plenty of room. My over-sized [vastly over-sized] skimmer from the 150 that I will use has a suggested operating height of 7-9 inches, so I'll have at least 8 inches to work with if I make the first baffle 10" high and use a pedestal - more if I put the first baffle at 9". Definitely won't be worried about overflowing the sump tank as long as I keep my return line at a reasonable depth from the water line.

 

[Porpoise Hork]

So with a siphon break, really you only need adequate volume for what would be entrained in the return piping?

Also, how does a ball valve prevent siphoning? Or is that just for manually closing the line?

A siphon break is what you would use on the drain side of the tank to start/stop the overflow when there is a loss of return flow.

The one way check-valve is what stops siphoning on the return side. The ball valve would ideally be placed between the tank and the check-valve to close the line to the tank from the pump in the event you need to service the pump, clean the check-valve, and/or sump itself.

 

[LbulletM]

So taking a quick 90 degree turn here.... is a half inch around all of my equipment (skimmer, pump) sufficient?

 

[LbulletM]

I think I could pull this off with a 20L instead of a 29. Since they're the same footprint, if I make the first baffle only 8", I would have 4+ inches of vertical space.

Also, I'm impatient and don't want to wait for another $/gal sale....

 

[Porpoise Hork]

It really depends on multiple factors. How large the tank is. How many times you want it to turn over in an hour. The distance from the pump to the return jets.

A 1/2 pipe can only flow about 14 gpm or about 840gph. This is on a straight pipe with no bends. Add bends and this starts to drop. If you have say a 75G tank you want it to turn over at least 10 times an hour. So you are already nearing the max capacity flow rate for the pipe diameter. Next you need to factor in head pressure on the pump. To get the flow rate needed you will have to run a pump capable of at least 1000gph with a minimum 10' riser level. This is typically calculated with a pipe diameter at least equal to the pump outlet. Most return pumps have a 1" or greater outlet on them. So by running a 1/2" line you are doubling the head pressure and restricting the flow significantly. In order to compensate for this you would need to run a much larger pump to handle it.

You would be better to run at least a 1" ID pipe from pump to return jet and get a pump that is rated for at least 25% more than the max flow you need to get the desired turn over. If you get an A/C pump you can use a gate valve to restrict flow to the tank. Or you can use a DC pump and dial in the return flow rate. It takes some time and fine tuning to get it all in balance but once you have it set you should not have any issues.

 

[LbulletM]

Pssst, Chemical Engineer.

It's only a 29 gallon tank as I said above haha.

And I meant half inch between equipment and baffles? Not sure if that would make it basically impossible to get stuff in and out or not.

Dropping from a 29g sump with 14.7g of volume and ~14.3g of overflow space to a 20g sump would suffer a 3.2g volume hit and leave ~8.5g of overflow capacity. Is 8ish gallons of overflow for a 29g tank reasonable, or excessive?

 

[ryeguyy84]

don't forget about future pump upgrades. I like to give a little extra space.

I'm changing pumps right now and when I was measuring I just kept saying to myself i'm so glad I made this a little larger than needed.

 

[LbulletM]

don't forget about future pump upgrades. I like to give a little extra space.

I'm changing pumps right now and when I was measuring I just kept saying to myself i'm so glad I made this a little larger than needed.

The next pump upgrade will come with a full system upgrade But very good point!

 

[jason g]

For my sump, the return section has to be large enough to take the back-flow of water when the pumps are turned off. When I designed by sump, I calculated the back-flow volumes and that helped in the size of this section, and the location of the ATO float switches. Here's my sump, with the return section in the middle, and shared with the biopellet reactor.

I also run my return in the middle with the refugium to the right and my skimmer to the left. I can control the return flow on both sides. [emoji16]

 

[Kayotic5011]

I went 6 baffles made this from a 40 gal breeder, I have a reactor on it running phosguard as well....My pump is 1000+ gph but even with the area i gave it i dont seem to have a problem keeping water flow even. Granted its remote controlled and I have it around 85%...But none the less its fine, its got 16 inch long x 5 inch wide area to contend with....I wont lie though, if you have the pump all the way up it can suck that area dry if you let it.

 

[LbulletM]

Haha my biggest issue is that the skimmer has a 12.4 x 10 inch footprint!