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Thread: Return and drain monitoring question

  1. #1
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    Question Return and drain monitoring question

    I have a 180 gallon reef tank with 2 x 1" drains that are routed separately to my sump and 1 x 1" return that is split into two at the tank. I just recently added a 1" flow sensor to the second return so now I have flow sensors on each drain and on the return. I had only been monitoring one drain prior.

    I'm seeing some odd results and wanted to see if they were normal. The return sensor is saying I'm returning 771 GPH to the tank but one drain is measuring 531 GPH and the other 892 GPH for a combined 1423 GPH. I would have thought that the amount of water I return to the aquarium would be around if not equal to the amount I'm draining? Am I correct in assuming this? Do I have a problem a with my return sensor or do these results seem normal?

    Thanks,

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    Have you specified the correct flow sensor to the configuration?

    All the best,
    Rui

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    Quote Originally Posted by Rui Manuel Gaspar View Post
    Have you specified the correct flow sensor to the configuration?

    All the best,
    Rui
    Yep. They are set correctly at 1" inch and obviously GPH.

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    Where in the drain are the sensors placed? Wouldn't the drains also have a certain amount of air drawn with the water so actual volume would be skewed higher? The return piping would not have air associated and so a more accurate reading is assumed. Without knowing your plumbing my theory is only that.

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    Quote Originally Posted by azsoccerpop View Post
    Where in the drain are the sensors placed? Wouldn't the drains also have a certain amount of air drawn with the water so actual volume would be skewed higher? The return piping would not have air associated and so a more accurate reading is assumed. Without knowing your plumbing my theory is only that.
    +1 on this. Flow monitoring is not super reliable when there is a lot of air mixed with the water and is likely to jump around a bit. You could use a VO with a defer for alarming so it has to be below your target flow continuously for X amount of time so you don't get alerts from spikes when a bunch of air enters the line.

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    I didn't think of this. The sensors are placed in the basement about 4 feet from the overflows. I guess this makes sense. If I feel adventurous, I will try and swap the sensors around to make sure they are reading properly.

    Thanks guys.

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    Quote Originally Posted by stre1026 View Post
    I didn't think of this. The sensors are placed in the basement about 4 feet from the overflows. I guess this makes sense. If I feel adventurous, I will try and swap the sensors around to make sure they are reading properly.

    Thanks guys.
    You may get more accurate readings if you are able to bleed out the air and place the sensor after that. I have seen some examples where a T straight up provides a path for air to escape and allow the water to keep running. Your most accurate reading would be a horizontal run as close to the downturn into your sump as possible. Otherwise I would not be so literal in the math and rather use the numbers you are getting on your drains as the norm against any alarms you may want to put in. If you get a drain showing a norm of 850-875 gph then use that to set your alarms with a bit of leeway.

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    Thanks. Unfortunately, there is no horizontal run at all. The lines go straight down into the sump. However, it's not a problem. I was just checking to see if I should look into getting a new flow sensor for my return because I'm never happy with the flow I'm getting from my DC return pump

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    What type of drain configuration do you have setup o the tank? Is it gravity fed, Durso, Herbie, Bean animal, etc? I ask because if you are using a drain type that has a siphon drain with a valve and an emergency drain then you can place the sensor on the siphon drain above the valve and it will give you an accurate reading. The other drain would still have air and be all over the place.

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    Why not put them in the line up to the tank, because thats the same rate it will come down.

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    The drains are typical durso drains so I don't have that option.

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    Quote Originally Posted by Engloid View Post
    Why not put them in the line up to the tank, because thats the same rate it will come down.

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    Not sure I follow you. The sensors are in the lines going to the tank.

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    Quote Originally Posted by stre1026 View Post



    Not sure I follow you. The sensors are in the lines going to the tank.
    He's referring to using only the Return since this would be equal to the total drain flow unless both drains clogged. From strictly an absolute flow measurement I agree that the Return pump is the only important one, but setting alarms that the drains are well below normal ranges is very useful so I wouldn't get rid of them for sure.

    You might be an engineer if...You have no life and can prove it mathematically.

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    Oh! I get it now. Yes. That's what I'm doing currently. So he answered my question. The flow going to the tank should be equal to what's being drained which is what I thought.

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    Your tank is like a bucket that is full. If you pump ten gallons into it, ten will come out. Therefore, if you measure what comes out, you will know what was put in. If you have a clog in the drains, and want to be aware there is a problem....your sump will lower in level, and you can set alarms on that with float switches.

    Anither option may be to put a trap in the drain line and put the flowmeter in it.

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    I have a flow sensor installed on a full siphon drain, gravity drain, and return. I can confirm that the gravity drain never reads accurately due to the fact that there is air mixed in with the water (it will read artificially high). I would say it's still useful in that you can still set an alarm to receive alerts if the flow rate drops to something like < 200 GPH. That said, my apex decided this morning that no flow was going through either of my drains so I've been getting alerts all day that both drains are clogged, despite this not being the case.
    180g reef with all the bells and whistles

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    Frequent Visitor LobsterOfJustice's Avatar
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    Quote Originally Posted by Engloid View Post
    If you have a clog in the drains, and want to be aware there is a problem....your sump will lower in level, and you can set alarms on that with float switches.
    The problem with this is that there are a lot of things that could cause a low water level in the sump... skimmer or filter socks overflowing, topoff failed, leak in sump or other external equipment such as reactors... When you're on vacation and start getting emails that the sump level is low I'd like as much information as possible in diagnosing the issue.
    180g reef with all the bells and whistles

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    The better way to detect loss of drain with floats is to put high level floats in the overflow chamber. When that level is high you can be certain either a drain is clogged or your float failed. As lobster mentioned sump level isn't reliable, but overflow floats or FMM in drain pipes is pretty reliable.

    You might be an engineer if...You have no life and can prove it mathematically.

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    Frequent Visitor LobsterOfJustice's Avatar
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    I don't have an overflow box (drains are located directly in tank)... hence the direct drain flow monitoring.
    180g reef with all the bells and whistles

  19. #19
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    Quote Originally Posted by LobsterOfJustice View Post
    I don't have an overflow box (drains are located directly in tank)... hence the direct drain flow monitoring.
    Do you have just pipes through the goass?

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  20. #20
    Frequent Visitor LobsterOfJustice's Avatar
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    Yes I have bulkheads directly into the tank.
    180g reef with all the bells and whistles

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