Are our sump turnover rates missing a factor?

[UncommonSense]

I know, I know… Sump turnover rates are a topic that’s been discussed to death…

But, I’ve been thinking…

I believe the general consensus of sizing your sump return pump to turnover DT water 3-5X max per-hour might be too generalized…

Before you start sharpening your pitchforks… let me explain!

This 3-5X turnovers per-hour benchmark takes no account for sump dimensions; specifically water height, and chamber dimensions…

To clarify: we’re shooting for a target amount of contact time, or dwell time of water in each stage of filtration within the sump. That we can all agree upon!

But, our generalized turnover numbers don’t assume tank dimensions vs. sump dimensions! — that is to say; 1000gph moving through a sump chamber with a 12”X8” water column cross-section happens twice as fast as a 24”X8” sump chamber water column cross-section…

This means a 18” deep sump at 12” water height has 2.25X more filtration contact time than a 12” deep sump at 8” water height; both using the exact same flow rate.

Thoughts? Questions? Interesting ideas?

 

[exnisstech]

Ignorance is bliss. I couldn't tell you what my turn over rate is in any tank I have ever run. I adjust the return to make the overflow as quiet as possible and I set the in tank flow by looking at coral and how food blows around. Coral snow can be useful also. As far as actual numbers, meh I don't really feel a need.

 

[Yodaman]

I know, I know… Sump turnover rates are a topic that’s been discussed to death…

But, I’ve been thinking…

I believe the general consensus of sizing your sump return pump to turnover DT water 3-5X max per-hour might be too generalized…

Before you start sharpening your pitchforks… let me explain!

This 3-5X turnovers per-hour benchmark takes no account for sump dimensions; specifically water height, and chamber dimensions…

To clarify: we’re shooting for a target amount of contact time, or dwell time of water in each stage of filtration within the sump. That we can all agree upon!

But, our generalized turnover numbers don’t assume tank dimensions vs. sump dimensions! — that is to say; 1000gph moving through a sump chamber with a 12”X8” water column cross-section happens twice as fast as a 24”X8” sump chamber water column cross-section…

This means a 18” deep sump at 12” water height has 2.25X more filtration contact time than a 12” deep sump at 8” water height; both using the exact same flow rate.

Thoughts? Questions? Interesting ideas?

I think you have a good train of thought, but it should also depend on what is in each chamber and the specific goals intended in the sump

 

[UncommonSense]

As far as actual numbers, meh I don't really feel a need.

I think it’s an important consideration! We’re talking upwards of 500% differences in fluid contact time, depending on chamber layout… that’s a massive skew to the standard formula!

I think you have a good train of thought, but it should also depend on what is in each chamber and the specific goals intended in the sump

My thoughts precisely! That said; the length of the chamber isn’t a relevant factor for contact time with an individual sample of the moving water… it would purely be dictated by the width and height of the water column, versus nominal flow rate through the whole sump!

This math points towards AIOs being remarkably inefficient!

 

[exnisstech]

Like I said ignorance is bliss ;) And I suck at math.
If AIO are inefficient there are an awful lot of nice looking inefficient tanks running lol.

 

[F i s h y]

I think it’s an important consideration! We’re talking upwards of 500% differences in fluid contact time, depending on chamber layout… that’s a massive skew to the standard formula!


My thoughts precisely! That said; the length of the chamber isn’t a relevant factor for contact time with an individual sample of the moving water… it would purely be dictated by the width and height of the water column, versus nominal flow rate through the whole sump!

This math points towards AIOs being remarkably inefficient!

An additional note, in my refugium, the water tends to roll a bit, meaning that some of the water does exit fairly quickly from the refugium into the return chamber, but a portion of it actually cycles at least twice if not more. I'm not even sure how you would go about measuring that. Hydrodynamics are quite intricate.

 

[KStatefan]

In my opinion is does not mater. Our sumps are not a single pass system.

 

[UncommonSense]

An additional note, in my refugium, the water tends to roll a bit, meaning that some of the water does exit fairly quickly from the refugium into the return chamber, but a portion of it actually cycles at least twice if not more. I'm not even sure how you would go about measuring that. Hydrodynamics are quite intricate.

There really isn’t a good way to measure the increase in contact time there; just kinda find the average!

I was thinking about this aspect regarding my first reef tank’s sump… just a 20g tall with no baffles, and as much rock as I could possibly pack into it! — it ran at around 16.5” water height; so quite a bit of contact time there (on average) for a tiny system!

 

[Reefer Matt]

Ignorance is bliss. I couldn't tell you what my turn over rate is in any tank I have ever run. I adjust the return to make the overflow as quiet as possible and I set the in tank flow by looking at coral and how food blows around. Coral snow can be useful also. As far as actual numbers, meh I don't really feel a need.

 

[UncommonSense]

In my opinion is does not mater. Our sumps are not a single pass system.

I think it primarily matters in return pump sizing, and by proxy, price… secondarily for power consumption!

 

[UncommonSense]

Let’s also remember that many sump water heights are dictated by internal skimmer running requirements… the typical sump can hold more volume than the DT drains during a power outage/etc…..

Considering this; why not simply add a skimmer stand (if overhead clearance isn’t an issue), then run the maximum sump water height you safely can for increased filtration contact time?

 

[Aaron Stone]

I think it primarily matters in return pump sizing, and by proxy, price… secondarily for power consumption!

I think his comment was geared more towards the idea of worrying about contact time. As he said, it's not a single pass system, so why worry about contact time?

 

[Johnd651]

Let’s also remember that many sump water heights are dictated by internal skimmer running requirements… the typical sump can hold more volume than the DT drains during a power outage/etc…..

Considering this; why not simply add a skimmer stand (if overhead clearance isn’t an issue), then run the maximum sump water height you safely can for increased filtration contact time

Sump water height ... so I also count on my sump to take back some of the water in the piping during a power outage, hence leaving room for height.

 

[UncommonSense]

I think his comment was geared more towards the idea of worrying about contact time. As he said, it's not a single pass system, so why worry about contact time?

Because the return pump itself could be sized either larger or smaller to make better use of the specific sump design (vs sizing return pumps off the current generalized formula), and potentially yield long-term power savings!

 

[UncommonSense]

Sump water height ... so I also count on my sump to take back some of the water in the piping during a power outage, hence leaving room for height.

This was addressed in the message above… also, consider installing an anti-siphon device if you’re having difficulties maintaining sufficient reserve sump volume during return pump shutdown or power outage!

 

[Reefer Matt]

I adjust the pump output (dc controlled) and main drain valve to regulate water flow for noise. A baffle in the sump provides the continuous height I need for the skimmer.

 

[UncommonSense]

I adjust the pump output (dc controlled) and main drain valve to regulate water flow for noise. A baffle in the sump provides the continuous height I need for the skimmer.

Absolutely! That is the most common plumbing/sump layout around…

I’m specifically looking at the dimensions of the sump, and its chambers/operating water heights vs. turnover rate through that sump! (Some sumps are wider than others, some sumps have deep refugium chambers, some sumps run 4-6” of water height, some sumps bisect a chamber longitudinally, etc…)

 

[Reefer Matt]

Absolutely! That is the most common plumbing/sump layout around…

I’m specifically looking at the dimensions of the sump, and its chambers/operating water heights vs. turnover rate through that sump! (Some sumps are wider than others, some sumps have deep refugium chambers, some sumps run 4-6” of water height, some sumps bisect a chamber longitudinally, etc…)

Gotcha. I just go old school. All my sumps are standard Aqueon aquariums with a baffle in them.

 

[UncommonSense]

Gotcha. I just go old school. All my sumps are standard Aqueon aquariums with a baffle in them.

Haha I build all my own sumps too; glass tanks, glass baffles!

There’s a lot of playing around you can do with this math… making three dimensional water flow through a sump, for example! (Think, water cascading from back half of a sump chamber to front half… [better sized internal skimmer compartment, for example])

 

[Aaron Stone]

Because the return pump itself could be sized either larger or smaller to make better use of the specific sump design (vs sizing return pumps off the current generalized formula), and potentially yield long-term power savings!

Ah, if it is for cost savings on a smaller pump that makes sense.