Does a sumps water height change?

[Quatro]

Hey,

I've been working on a central system with a common sump on the floor.  I just did a test and it is working ok at maximum flow.  One thing I noticed that seems odd, the water height in the tanks will lower by 1/2" and the sump will raise.  Then the tanks will raise and the sump will lower.  It keeps cycling like that.  Is it normal?  Thanks

[dan2x38]

I am no physics prof. but I am betting it has to do with the pressure created by increase in volume. When that occurs it would have more force so a little faster drain. Hence the flip side for sump decreasing. Grasping at straws but it sounds good... LOL

With this project I think you are the one who will have the answers your cutting new trail.

[redbelly]

No that is definately not normal.

Sounds like you overflow MAY be cycling between a full syphon thne breaking, then full syphon....

What size overflow do you have and what is your return pump?

[nelson]

I was thinking it may be the same thing.....air lock.  Does that make me almost as smart as you Patrick

[Quatro]

It is a 1.5" pipe (setup like a durso overflow). 
The return pump is a Mag18 (based on height I would say 1200 - 1300 gph)

The overflow pipe is sucking a lot of air.  It comes in on the side of the sump under the water level and is belching air bubbles constantly.  I'm making a change tonight to the sump water level.

[redbelly]

A single 1.5" drain?
You should always have 2.

That return pump is HUGE!
My return pump is 1700 GPH @ 0' Head and is pumping up with at least 15' of head pressure, feeding a fuge and I still have it throttled back by over half with a 4' internal coast to coast.


What overflow style do you use?
Is it a coast to coast overflow on a large tank?

If your running a single durso stand pipe with that much flow I would guarantee that it is cycling between a full syphon then breaking, then full syphon....

[Hookup]

The issue is definitely your flow-rates down are maxed out...or close enough to be very dangerous...  Easy way to test, if you can get your hand in there... is take 2 or 3 fingers and create a partial blockage in the return line... the main tank should start to fill, and if you do not watch it, overflow.... (remove "blockage" before overflow)

I've never been a fan of high-flow sump designs... I think a MAG 7 or so is the "normal" pump for under-tank designs giving around 500 gph return at 4 or 5 feet of head?

Anyhow... if you are keeping the higher flow, you'll have to find a way to allow more water to "GET OUT" of the display and into the sump.  IMO, you are one snail away from a flood.

[JetJumper]

+1 too much flow

I have a 1500gph pump that is throttled back about 50% with another pipe teed off to my Skimmer.  So maybe 400-500gph to my display and 500 to my skimmer.

[Quatro]

Thanks for the advice.  This is for my central freshwater system.  The setup is the sump on the floor, pump goes to 7 faucet style valves (each over a 20gal), whatever is left goes up to the next level (a 75gal) which has a water bridge over to the next 75gal, then a single durso overflow back to the sump.  I do not plan on running it at maximum but wanted to test at that rate to see if it could handle anything unexpected.  I would like each of the 20gal's to get 60gph.  That would leave 800gph for the top which I would throttle back to about 400gph.  The reason for the large pump is because I have room for a third 75gal which would also be run off the one pump.

[redbelly]

Is it too late to drill an extra hole in your sump?
2 x 1.5" bulkheads would certainly help solve your problem.

The same theory applies for building a fw sump or sw. The overflow style though dont matter as much of course.

[Quatro]

I could easily drill another hole in the sump but wouldn't I need a second in the display tank as well?  That could be a problem.

[redbelly]

I am just looking through your water bridge post here, it looks like the water comes in on the top left side of the tank, goes aross the water bridge, then down from 1 x 1.5" bulkhead on the right side correct?
And its this last tank that I am assuming the water level is changing on, and the overflow is making a lot of noise.

If this is the case, then drilling another hole in this tank would obviously allow you to run your current flow rate through the tank.
Either that or just the flow back to the tank.
It would be nice to have the high flow rate though for nutrient removal.

btw, have you changed the following plumbing?
As this is not considered a durso:

[Quatro]

I have changed it.  Most recent picture you can see it in the background.  I have lowered the durso an inch since this pic.

The water bridge is 6 inches diameter so the water levels stay the same (ie.  I see the water level raising and falling on both the 75gals).