Sump level fluctuations

[ilyad]

Hey everyone,

It's been a long time since I've had a tank and this time around I'm setting one up that has a sump. I've figured out the plumbing and all other aspects but noticed a small issue while doing a leak test...

After adjusting my water level in the return part of the sump, I let my tank run and it gets a small drop in the water level due to evaporation. Now I know this is normal. However, if I kill the return pump (as I would if I needed to do tank maintenance or other misc stuff) and then restart it again, the level in the sump will sit lower. This has happened on several occasions

I suspect this will be a problem because the level either doesn't go down far enough initially and the top off water wouldn't feed in enough (raising the salinity level) OR if the first is correct and the water drops below what it should be, there would be too much top off (lowering the salinity level).

Has anyone experienced this problem and can shed any light on what can be done?

Some specs:
25 gal display cube
5 gal sump (sump has 2 chambers - skimmer/in part and return/top off part separated by a chamber to trap bubbles)
Single return pump

Since the water capacity is so small the small change in the sump level would be noticeable when that happens.

Thanks in advance

 

[thehammer1985]

Does it sit higher in your tank ? Does it ever go back to where it was after several hours?

 

[TheEngineer]

That's normal. When there's more water in the sump the head height is slightly less and your pump can push a little more water. It should even out after some run time.

 

[twilliard]

Also the amount of air in the overflow pipe helps determine the the volume
I have a tube in my overflow that allows air to be drawn.
If I put my finger over the tube the flow slows down and drops my return section of my sump.

 

[ilyad]

Hmm... Thanks for the advice guys. My tank is only 25 gal and the sump roughly 5 so that small fluctuation I'd imagine would change the salinity a lot. Unfortunately I don't have room for a bigger sump to make the change more negligible with more water volume.

 

[ilyad]

That's normal. When there's more water in the sump the head height is slightly less and your pump can push a little more water. It should even out after some run time.

My question is if that's the case and I kill the pump and then run it back on, before it adjusts the ato would already dump ro water in. I don't have a control system to put it on a delay and would hate to have to pay that much just for that issue.

Is there any ideas to minimize that effect?

 

[TheEngineer]

Oh, I see what your concern is. You're worried that the small fluctuation in the water level in your sump will result in your ATO pumping too much water in?

You can rectify that fairly easily, IMO. Put the low water sensor just above the level where your return pump will suck air and then put the high water sensor at the correct fill level. You shouldn't even pump in top-off water unless your water level gets low enough to need it.

 

[ilyad]

Oh, I see what your concern is. You're worried that the small fluctuation in the water level in your sump will result in your ATO pumping too much water in?

You can rectify that fairly easily, IMO. Put the low water sensor just above the level where your return pump will suck air and then put the high water sensor at the correct fill level. You shouldn't even pump in top-off water unless your water level gets low enough to need it.

I have the Tunze ATO and the sensor keeping the level is a single laser sensor with a fail safe float switch. I'm not sure I can set it up the way you describe so that it tops off as the water evaporates.

 

[TheEngineer]

I don't know that ATO specifically, but they all have a "high" and "low" level in my experience. The high level tells it when to stop adding water and the low level tells it when to add water. You want the low level to be lower than the fluctuation you are worried about. For example, let's say your full return chamber is 12" tall and your pump starts to pull in air at 6".

If you get a fluctuation of say 2" when the sump is full when you restart the pump. You want to set the "low" value of the ATO to be at the 6.5-7" mark and the high value at 12". This way, even if you have a 2" fluctuation in the water level, that isn't enough to kick the ATO pump on.

 

[Diesel]

Can you post some pics from your overflow from the tank back into the sump and your return section to the tank?

 

[ilyad]

I don't know that ATO specifically, but they all have a "high" and "low" level in my experience. The high level tells it when to stop adding water and the low level tells it when to add water. You want the low level to be lower than the fluctuation you are worried about. For example, let's say your full return chamber is 12" tall and your pump starts to pull in air at 6".

If you get a fluctuation of say 2" when the sump is full when you restart the pump. You want to set the "low" value of the ATO to be at the 6.5-7" mark and the high value at 12". This way, even if you have a 2" fluctuation in the water level, that isn't enough to kick the ATO pump on.

Unfortunately the tunze doesn't have a high low set up. It only has a single laser sensor that keeps the level the same the entire time and a fail safe shutoff float switch in case the ato pump gets stuck to kill the flow

 

[TheEngineer]

Hmm. Well then I don't know what to suggest

 

[ilyad]

Can you post some pics from your overflow from the tank back into the sump and your return section to the tank?

Here is the current set up:

Overflow and return pipe:

Enkamat in the overflow to prevent gurgling:

Standpipe with FLUSH tube (provided by the overflow manufacturer):

Sump and reverse durso to quiet down the exit:

The reverse durso is done just like this one (hard to see mine in the pictures):

 

[ilyad]

Hmm. Well then I don't know what to suggest

No problem! Thanks for giving it a shot

 

[afamousjohnson]

So think about it like this - with the flux and it lowering the water - it adds top off to level - than as it levels its self out you now are above your sensor. Evaporation will bring you back down to the point where you just were previous. Now salinity is back to normal and it starts over again
Even in a small water volume - tho not the best of stable - you would think it would be a small fluxuation in salinity but always leveling itself back to normal right?
How big of a drop are we talking here? Right below the sensor enough to trigger or inchs?

Also there is a setting I believe with tunze where you can adjust the delay inbetween filling? Say if you have a bad fluctuation problem with water level - you can set it to after the 1st fill it wont activate again for x min

 

[afamousjohnson]

is that the normal level you run in your return section? When you shut down power and everything empties back down to sump do you still have extra space in sump for more water? If so maybe try highering the return chamber water level - I would be nervous of a failure in ato and not allowing yourself anytime to catch it with a low return chamber level like in the pic. Who knows might fix the previous prob also? My last tank did this and messed with both my jbj and tunze ato

 

[ilyad]

For those who are interested, I managed to resolve the problem by extending the bottom tube of the durso in the sump. Somehow that created or released the pressure so now when it's turned off and on, the water level returns to normal. Thank you all for feedback