Why???

[Vinny Kreyling]

When running a Herbie drain the water level in the overflow boxes keep fluctuating.
I am told this is normal but would still like an explanation as to why this happens.
In layman's terms please.:confused:

[ormet]

I dont think its normal.

But if your return pump does not sit in a water level controlled part of the sump you will get different head pressure for the return pump depending on how much water there is in the return pump compartment. This will make the return pump deliver different gph for the drain to swallow.

[Vinny Kreyling]

With ATO the pump section remains steady until the overflow boxes change.???

[TruReef]

I notice this too on my system. I think it has something to do with barometric pressure fluctuating, but have no evidence of this. I just set it where it won't overflow into the backup and leave it alone. A fine tune every now and again is necessary....

[jimmyj7090]

Same here, mine fluxuates a little, usually needs a slight adjustment monthly or so.

I've heard mention of barometric pressure but also can't explain that. Additionally any growth or fouling in the pipe could slow the drain flow, something getting caught in the return pump's impeller could alter flow a little. One way or another, a little fluxuation is normal.

[dixiedog]

I've seen it fluctuate on some tanks, while remaining rock steady in others. I have some theories, take them for what they are, just guesses.

Theory One: the return pump does not run at precisely the same GPH all the time. It would not take much fluctuation at all to cause a rise or fall in the overflow.

Theory Two: the voltage in the house does not stay 100% rock-steady all the time ... which could cause #1 to happen.

Theory Three: theories one and two are totally wrong, and I give up.

[ca1ore]

Probably your siphon pipe is either not of sufficient size such that the secondary is cycling between an overflow and a siphon; or, the siphon is too large and is cycling between an overflow and a siphon. If you set your siphon so that just a small trickle of water is going down the overflow, does the level then remain constant?

It would be helpful if you could describe how the level fluctuates, how often, and the specific details of your herbie. I have run herbies from before they were herbies, and if sized properly, they are rock solid.

It is necessary to periodically adjust the siphon on a herbie drain as buildups in the various pipes will affect flow over time.

[Vinny Kreyling]

1" overflow pipes, both drain & emergency on a 250 Gallon.
7 -8 inch differential between pipe lengths in each box.
Same lengths in each box.
Variations run as much as 7 inches in water height.
I do NOT want a trickle in the emergency pipes.

Running a DC pump so voltage "might play a role"

[jimmyj7090]

Almost exactly the same set up here.

IF I were to allow a trickle down the emergency it would surely SEEM steady on my set up but that's just because the fluxuations would show up in the volume of water trickling down the emergency which I'm pretty sure would be nearly un-noticiable to me.

I prefer to keep the dry emergency dry as well. In trying to do so I see a similar fluxuation across the 6" or so between the siphon and emergency standpipes. It happens slowly, no noticiable change day to day, but I still find myself adjusting the valve by a hair one way or the other about monthly.

[ca1ore]

If fluctuations in height are happening quite rapidly, then it is a pipe alternating between overflow and siphon. If the fluctuations are happening slowly, then is it simply a matter of dialing in the siphon more precisely. BTW, never have seen a particularly compelling reason to necessarily keep the emergency dry - lots of conceptual arguments, but none that hold much practical weight. I always ran my dual drains with a trickle in the overflow - only way I found to not have to constantly mess with it. I actually setup a float switch to tell me when flow through the overflow drain was picking up so I would know to check the siphon pipe.

[Vinny Kreyling]

One of the problems when the boxes get low is air in the drain tubes making noise.
When the water rises too much the braces in the tank appear in the water.
Wondering if the drain pipes could be shorter?

[jimmyj7090]

If the fluctuations are happening slowly, then is it simply a matter of dialing in the siphon more precisely.

I always ran my dual drains with a trickle in the overflow - only way I found to not have to constantly mess with it.

I'm confused, it sounds like you are contridicting yourself? If more precise adjustment will eliminate slow fluxuations, then why do you need to keep a trickle in the emergency to prevent having to "constantly mess with it"?

[ca1ore]

I'm confused, it sounds like you are contridicting yourself? If more precise adjustment will eliminate slow fluxuations, then why do you need to keep a trickle in the emergency to prevent having to "constantly mess with it"?

Well, more precise adjustments will reduce slow fluctuations but never completely eliminate them - too many variables at play. I found that keeping the emergency dry most of the time required me to regularly adjust the gate valve on the siphon - by regularly I mean every week or so. If, however, I set it so that I just get a trickle through the backup, then I ended up needing to look at it monthly.

[jimmyj7090]

Well, more precise adjustments will reduce slow fluctuations but never completely eliminate them - too many variables at play.

Ah, gottcha, and agree.

[ormet]

Oh i might have misunderstood OP, some smaller adjustments are necessary due to many reasons as you have been told already.

But properly set up i adjust maybe bi-weekly.

[dixiedog]

I might adjust mine once every three or four months.

[mc-cro]

I ran a herbie for about 8yrs. occassionally, like once every few months I would have to put about a 1/8turn on the gate valve to adjust the water level.

For me, I found I HAD to run a very small trickle down the emergency drain. that allowed for the fluctuations to be in the that pipe, instead of the main drain. The emergency drain was above water leve in sump, so I could see or hear if it was taking too much water.

[mr.maroonsalty]

I run pipeless bulkheads and dump both 1" into a 1 1/2" horizontal pipe so I only have one adjustment. I also use a 1 1/2" bv for the main adjustment, but have a 1" gv wye-ed in for fine tuning, and it actually saved a couple bucks over a 1 1/2" gv. Water over my overflows will crash if the water in the box is too low, so I keep the level right up near the standpipes, depending on the weather, or whatever it is, I might tweak my fine tuner everyday then go a week or more without touching it. I could see having gradual big fluctuations because the syphon is letting a small amount more than perfect balance out if the sound of water falling over the bulkheads or trickling from the em didn't bother me. Could always go with a submerged backup pipe and a slight trickle, but then I couldn't hear if it is more than ever so slight a trickle either.