Sump Flow Question

HI all,
I have a question with regards to water flow in the sump. Well let me start by saying that I have lots of tanks, but none are filtered with sumps even my big tank. I just upgraded one of my 55's to a 120 RR tank. So far I regret doing so, cause I can't seem to get rid of the micro bubble and can't seem to get really good mechanichal filtration without restricting my pump outflow drastically (which lowers my water level in the pump chamber). I have researched quite a bit on sumps (but still very naive when it comes to designing them) but I think that I have designed my DIY sump wrong, at least when it comes to the flow in the sump. I design the sump as a channel flow that starts at one and and circles around to the same end but opposite corner. The overflow drops at the back left corner and my pumps sits on the front left corner. I have a standard 20 (24"L x 16"H x 12"D) gallon tank (it was the only one that would fit under the stand) for the sump. The question that I have is complicated to answear as it might depend on the way the sump was designed, but I woul like to ask it anyways. What should my flowrate be in the sump this size? and hope to prevent the microbbubles and water level issues that I have once I place mechanichal filtration media. If anyone has thoughts on this, I would greatly appreciate it if you shared them with me.

Thanks

 

Flowrate depends on how much and what kind of filtermedia you have as it is really a function of how much surface area you are running the water over in a given amount of time. The standard "cannister filter" flow rate is usually given to be about the volume of your tank 5x/hour, but cannisters are usually filled with filter media designed to have extraordinary amounts of surface area/volume. They can also pack that media tighter than we sump-users can because they have more water pressure to force the water through.

Microbubbles are usually dissipated using relatively tightly spaced baffles...from your description I'm not sure that you are using baffles at all so the entrained water lightly doesn't have time to dissipate.

Water level issues...if the the sump is able to sustain the water flow you want without media, then chances are your media is not permeable enough for sump use, which is a common mistake (and one I've made). As nice as it is to use the fancy pads that scrub microparticles from the water, the unfortunate thing is that without the additional water pressure sustained in a cannister, the only way to use them in a sump is to have a sufficiently low flowrate to allow the water to pass through, and/or a large section of the cloth to give more surface area for water to pass through.


Kinda babbly because I'm in a hurry but I hope this helps a bit.

 

Flowrate depends on how much and what kind of filtermedia you have as it is really a function of how much surface area you are running the water over in a given amount of time. The standard "cannister filter" flow rate is usually given to be about the volume of your tank 5x/hour, but cannisters are usually filled with filter media designed to have extraordinary amounts of surface area/volume. They can also pack that media tighter than we sump-users can because they have more water pressure to force the water through.

If I understand the canister filters correctly, they act more like a closed loop than an open one, right? The sump is open loop, right? If so than the ristrictions in the canister filter does not really matter as the water being succked out of the tank is what comes out of the naister filter and back into the tank. Thus the flow rate does not affect anything other than it will move less water.

Microbubbles are usually dissipated using relatively tightly spaced baffles...from your description I'm not sure that you are using baffles at all so the entrained water lightly doesn't have time to dissipate.

I do have 3-sets of baffles. The first one is a single one that is right after the inlet of the sump (the water leaving the DT and coming into the sump). This baffle is about 1" in width. The second set is more like chambers that allow for media to be placed and they wrap the tank at the other end (they make a 180 turn). On the back right corner is one of the baffles (chaimber) that is 3"x7" and feeds into another baffle (chaimber) that is 3"x5". The third set is just before the return pump and there are 2 baffles that are again around 1" in width. The water flow through the sump is channel froma 7" wide to a 5" channel that are of different heights as the flow goes thought the sump. The highest level is around 11" at the inlet and in the first main chamber of the sump (where I have sand and live rock, similar to how wet/dry sumps have bio-balls) than it drops to 10" into the second set of baffle and second chamber (refugium for later, with DSB). Than there is the 3rd set of baffles that consists of two 1" chambers that allow for bubble difusion.

Water level issues...if the the sump is able to sustain the water flow you want without media, then chances are your media is not permeable enough for sump use, which is a common mistake (and one I've made). As nice as it is to use the fancy pads that scrub microparticles from the water, the unfortunate thing is that without the additional water pressure sustained in a cannister, the only way to use them in a sump is to have a sufficiently low flowrate to allow the water to pass through, and/or a large section of the cloth to give more surface area for water to pass through.


Kinda babbly because I'm in a hurry but I hope this helps a bit.

Yeah, and that's part of the problem that I have. When I place the pads the flow is restricted so much that the level in the return pumps goes so low that when the water evaporates it might allow for the pump to run dry. I have tried placing it in different areas but at the end I get the same result. I am thinking that I might have to take the sump out and make a custom one (that is bigger and allow for more volume in the return chamber) cause I would not want to go to a smaller pump, unless I can figure out how much flow I can run through the sumop with no problems. I have posted this question, but seems it might have tocome to trial and error to figure that one out. Either way thanks for your imput.

 

Keep in mind that Freshwater wet/dry and Saltwater sump although similar in construction work differently. The Freshwater sump usually operates with a smaller volume of water than a Saltwater sump/fuge.

I figure you need to build a bubble trap (which is achieved easily with three baffles). Please google info on this simple idea. An easy way of looking at this is that the return pump rate must balance out with the intake flow, otherwise you'll sump will work towards either drying out or flooding. The maximum flow on the intake will determine the maximum flow rate of the return pump (compensating the head loss).

If your only problem is microbubbles, then you already achieved that balance. I place the return pump at one extreme of the tank, then I used three glass (acrylic works) sheets that I kept around 1" apart from each other, with the middle one leaving one to one-half inch space towards the bottom while the ones at the sides are attached to the bottom work nicely well. I have no bubbles in my DIY sump.

Pepetj
Santo Domingo

 

Keep in mind that Freshwater wet/dry and Saltwater sump although similar in construction work differently. The Freshwater sump usually operates with a smaller volume of water than a Saltwater sump/fuge.

Not sure what you mean by differently. But all mechanichal filters (canister, hang on the back, sumpa, wet/dry, trickle and many more) work the same way. You pass a stream of water through the media ro filter particles from the water column. The media will determine the final flow rate of the filter. Which is in part the problem I am having. The filter pad is not pourus enough to let enough water through without draining my return chamber too much.

[/QUOTE]I figure you need to build a bubble trap (which is achieved easily with three baffles). Please google info on this simple idea[/QUOTE]

As stated above I have 3 sets of baffles to trap bubbles, but the flow rate going to trough the sump is too strong. The flow becomes turbulant and it creates additional bubbles. Which leads to the quetion at hand, how can I figure out what the maimum flowrate that a sump can handle? I am thinking it's going to have to be a trial and error type of scenario to figure that out, or look more into fluid mechanics.

An easy way of looking at this is that the return pump rate must balance out with the intake flow, otherwise you'll sump will work towards either drying out or flooding. The maximum flow on the intake will determine the maximum flow rate of the return pump(and any other restrictions that the sump may have) (compensating the head loss).

That is correct now, what determines the maximum flowrate through the sump. I know it has to be a function of retrictions, like filter pads, o-rings, foam stars, ceramic cylinders, carbon filled socks or and any other media that can be used. It also has to do with the size of the spacings between baffles and any other opening that the water is flowing through. I feel that is giong to be more complicated than just using some other type of mechanichal filtration.

If your only problem is microbubbles, then you already achieved that balance. I place the return pump at one extreme of the tank, then I used three glass (acrylic works) sheets that I kept around 1" apart from each other, with the middle one leaving one to one-half inch space towards the bottom while the ones at the sides are attached to the bottom work nicely well. I have no bubbles in my DIY sump.

Pepetj
Santo Domingo

If you buy a sump pre-made by a manufacturer. Thye will rate the sump filter for a specific size tank just like they do for hang on the back filters. If you wanted to find out what the maximum flowrate through the sump (pre-made), how would you go about figuring that out (I do belive that is independent of the tank, and more dependent on the restrictions as mentioned above)?

 

Thankyuo all for the info. and help. I am finding out that it's too much of a headache (trial and error) and costly to make my current sump work right. Thus I am going back to the drawing board and rethink my whole mechanichal filtration sytem. Thanks for the help.

 

So I am considering a sump for my 75 g community tank. I just need to understand the basics first before I put pen to paper and flood the house. From what I have read this is my understanding;

The outlets from the tank must, under gravity, be able to drain into the sump slightly more volume than the flow rate of the pump?

When the pump ceases to pump that the the reserve capacity in the sump must be able to hold the inrush of water from the draining of the tank to the bottom level of the outlet pipes, as well as the flow back from the inlet and outlet pipes to and from the main tank?

Anyone got a flow chart for PVC pipes?

 

I built a tank and sump from scratch with acrylic sheet. As long as the pipe from the overflow can drain quicker than the pump rate it doesn't matter by how much. I just used 40mm pipe which could probably take 10 times the flow required. The hardest part to source was the bulkhead fitting that connects the return to the hole in the tank. Don't buy tube until you know you can get the fitting in the same size

 

I have not arrived there yet (it is my dream to have a big aquarium with sump), but what I have understood:

1. you need to match the outlet with the inlet, otherwise you will have trouble with maintaining the water level in the tank; you can do this by having ball valves on the tubing; I would match the pump size to the flow you want to have in a 75 gallon...

2. you are right for the stopped pump scenario! however, you can break the siphoning effect by drilling a hole on the tubing right below the water level in your tank - about half an inch below... still, leaving some extra room in the sump would be a wise idea...

One question: why do you think that a sump would be a better idea on a 75 gallon than one or two canister filters? (just curious)

 

Thanks, I hear you on the bulkheads. The guys in the U.S. appear spoiled for choice, we really struggle here.

 

I have not arrived there yet (it is my dream to have a big aquarium with sump), but what I have understood:

1. you need to match the outlet with the inlet, otherwise you will have trouble with maintaining the water level in the tank; you can do this by having ball valves on the tubing; I would match the pump size to the flow you want to have in a 75 gallon...

2. you are right for the stopped pump scenario! however, you can break the siphoning effect by drilling a hole on the tubing right below the water level in your tank - about half an inch below... still, leaving some extra room in the sump would be a wise idea...

One question: why do you think that a sump would be a better idea on a 75 gallon than one or two canister filters? (just curious)

I suppose from my reading there are a many advantages;

- You can add your accessories in the sump, heaters and air stones which drive me nuts in the main tank.
- You can add medication to the sump which can be evenly dispersed by the pump.
- You increase the amount of water available to the fish. I am planning a small sump 18g or 24% so I effectively have a 93g tank.
- You can change filter media without having to switch off the pumps and clean.
- You can increase the amount of filter media based on the size sump one chooses.

Cheers

 

Thanks!

I can agree with the filter maintenance and increasing the water volume!

But the heater and airstone part can be mounted inline, on the return of a canister filter... I'm not really medicating the main display tank - that's what the quarantine tanks are for... if still needed, then just drop the medication in from top the water outlet...

Also, I doubt in that a 18 gallon sump, with the safety volume, can hold much more media than two appropriately choose canister filters...

Bottom line: although I am dreaming of a sump filtration, I wasn't thinking on such small aquarium... so, thanks again for sharing your thoughts!

Regarding to the tubing size, based on what the King of DIY says:

"The overflow simply needs to be able to flow more than your pump. What this means is if you have a 500gph pump, you will need at least a 500gph overflow. For safety reasons I suggest using double size you need."

Also from his book, regarding the tubing and flow:

0.5" = 90gph
0.75" = 220gph
1.0" = 375gph
1.25" = 580gph
1.5" = 840gph
2.0" = 1500gph

 

You should be able to find gravity flow rates for pipes online. It's a common enough thing in all kinds of industries where fluids are used.

I have to disagree with Zka17 about media volume between sump and canisters. You'd have to move into pond filters to find one canister to compete with even a 18 gallon sump, so you're probably looking at two canisters. At least one issue there is duplication of media. If you put biological media in both canisters, you have to protect it from gunking up by using mechanical filtration up front. Even if the sump only gives you equal total volume for media, you'll need only half the mechanical filtration, which leaves you with that much more room for biological media.

Figure one third the volume split between initial settlement chamber and return pump, one third for mechanical foam, and one third for biological media. You should easily be able to get four gallons of bio media in there, which should be way more than enough for your 75 gallon tank. You'd also have room for way more mechanical media than you'd get in two canisters, so it would end up doing an even better job of protecting the bio media.

 

But the heater and airstone part can be mounted inline, on the return of a canister filter... I'm not really medicating the main display tank - that's what the quarantine tanks are for... if still needed, then just drop the medication in from top the water outlet.

Correct but much easier if in a sump.

Also, I doubt in that a 18 gallon sump, with the safety volume, can hold much more media than two appropriately choose canister filters.

You are citing my choice of sump size. Sumps in general are normally larger proportionately.

Regarding to the tubing size, based on what the King of DIY says:

"The overflow simply needs to be able to flow more than your pump. What this means is if you have a 500gph pump, you will need at least a 500gph overflow. For safety reasons I suggest using double size you need."

Also from his book, regarding the tubing and flow:

0.5" = 90 gph
0.75" = 220 gph
1.0" = 375 gph
1.25" = 580 gph
1.5" = 840 gph
2.0" = 1500 gph

Thanks

 

I have been googling, every gravity flow rate table is different, and not by a small margin.

Can anyone confirm which numbers to use?

 

I have always just been under the impression my Aqueon Mega overflows moved aprox 750GPH per outlet .
This has always worked for me ..
IMO you use the largest drain you can and then get an adjustable pump and all will be well.
I run 3 sumps now ; on my 75 gallon palafarium ,my 120 marine and my 180g tank in my livingroom with sump in basement .
I highly recommend Jeboa DC pumps ..