He just wants to try out another different skimmer. After thinking about it I think
StirCrazy has hit the nail on the head....
Bill

Like I said earlier in this post that it is a plumbing issue.

Actually I have been diagnose with PTSD disorder from all of my tours. And this last tour kicked it higher causing me to take relaxing meds after certain incidents.So thanks sometimes when peoe makeacrack thinking it a joke
it's not

my sump did that to me once something clogged the overflow temporarily then it took off and went normal. so i say a plumbing prob maybe a snail in overflow turns one way its ok turns another and stops the flow.... or water gremlins all the same inthe end

I'm thinking the same sort of thing lockrockie is suggesting. Barring the possibility that someone might be topping up that you don't know about, it sounds more like to me that the speed of water in the overflow pipe is not steady state. If it speeds up the main tank drains faster until it reaches steady-state again (but by then it's lowered in the main tank, and we could be talking a minuscule amount for the level to lower for it to be substantial in the sump), and more water ends up in the sump. If it slows down the main tank drains slower until again steady-state is found and now the sump is low.

Things that can cause speed to change in the overflow plumbing are things like excessive bends that are prone to clogging (ie., snail in the pipe or whatnot), or even if the outflow pipe is submerged, it could be building up backpressure. Is there any "burping" happening where water enters the sump?

Another Oddball suggestion, but depending on how the restaurant's wired there could be a voltage drop when the lights and everything else are on in the tank, and also the restaurant. There's obviously building codes that would provide sufficient wiring with no more than 5% drop, but... if the tanks pigtailed off another circuit that's feeding something else, there actually could be 10%+ drop, reducing the output of the return pump.

I had this happen with 2 portable AC's plugged in to the same circuit as my tank, also finding out that 15A breakers can take a little more than what they say haha. But my water level in my tank was changing by 1/2 an inch when the AC was on, and off again the water would come back up. Turns out i had 102V at the receptical, and 112 with just the tank. This is >5%, and also in a new house, which should be to electrical code.

I agree with the others, probably a plumbing issue, but an easy test if you have a multimeter.

I don't know that I have said this before but..................... PLUMBING PROBLEM....................I have seen this tank in person once and got a quick look at the gut's and did not like what I saw. There was to much piping there for how simple the set up really is. Return line's are coming out of the overflow, there was a TON of hair algea at the top all around the overflow. I could not tell what the overflow consisted of because the resturaunt was open and I don't think the owner would have been to happy with me if I got down on the floor and got right into the sump area to check it all out. I did not really see a proper ATO, there is a second holding tank that is under the MD for RO water holding and it is plumbed at the bottom of the RO tank to the bottom of the sump.

Just my 2 cent for what it is worth.

I don't think he was trying to make a crack at you. I think you have tried out more skimmers than anyone else on here. sorry to hear about the PTSD I hope the meds work for you. My dad had a meltdown after Korea. Almost killed some guys back here at home.. Wars do wicked thing to your mind. I tip my hat to all of you guys that have gone over seas and fought either for our country or to help another country. I tried to get in to the military a few times scored very high on the entrance testing. But with asthma they will not take you at any rate. I had a base commander go up the ladder and try too get me in.. I even challenged the doc to some war games he picks a team and I would bring my own team we live in Winnipeg and I said it would be at CFB Shilo, He would not go for it. I was born there I was suppose to be the first new years baby, didn't happen I didn't want to come out for a few days. The base still had a party for my parents as it was the closest to date, that was in 1967....

Bill

maybe its tied into the toilets every time someone flushes... which still makes it a plumbing problem.

saying "its a plumbing problem" is not realy helping.

I said plumbing problem also, but pointed to a specific problem.
I know thoues of us who have built our reefs know instinctivly where to look, but think of this as what would you check in a system that you have never seen befor.. which also makes it alot harder not seeing it.

my guess as I said is a syphoning problem (which is a plumbing problem :mrgreen:) but who can say for sure never seeing how it is plumbed. is it syphoning in the overflow system, the skimmer ect? I had a skimmer that would do that.

some good pictures showing the set up and how its plumbed would go a long way to getting help figguring this out.

check to make sure the skimmer discharge is not submerged and if it is there has to be a high point for air to get into the discharge line to act as a syphon break or you will create a syphoning cycle in the skimmer.

Steve