Overflow siphon question

lar

lar

Member
I have my first tank that is not drilled and I'm thinking I would like to go back to a Sump.
In a gravity feed overflow, flow rate is self correcting, Any size Pump can be used for the return if your using a standard 1" drain.
Is this the case with a siphon? In my mind's eye I'm having a hard time seeing it.
What happens if you lose the siphon, does the return pump empty the sump into the tank, cound result in a overflowing tank? If the sump is big enough. Power loss I assume you would lose the siphon as soon as the level dropped below the teeth. But if you were not home, what then? Pump kicks back on and no siphon. ?? or does another pump create the siphon.
Any recommendations for a configuration? i.e. Pump/pipe/overflow
I like big sumps and big return pumps, less power heads that way.
120gal tank
Thanks
:help: :confused: :confused:
 
trigger16

trigger16

Member
Siphon doesn't break if your tank levels drop. The water still sits on the U tube until the water level in the tank go up where it continues to drop it to the sump.
What normally happens in these cases is power goes out and pump no longer works. So the tanks water keeps dropping to the sump until it stops by the overflow box. That is why you need to set it up where if the pump fails the sump can hold all the excess water from the tank. Bigger sumps work best for this.
Also what is worse at this is people do not attach a check valve on the retun line and normally this causes the tank to also drain down from that line that is usually lower than the overflow. Thus even more water going down.
As safety always use a check valave along the return line. I even go as far as drilling a tiny hole just above normal water surface of the return line (in the tank) in case the check valve fails.
Drilling the hole is very important as it has saved me numeorous times. Where I live we have many power outages as I live out in the woods.
When plumbing tanks always sit down and go over each pipe over and over again thinking worse case scenarios.
 
bigmac

bigmac

Member

Originally posted by Lar
In a gravity feed overflow, flow rate is self correcting, Any size Pump can be used for the return if your using a standard 1" drain.

Well, kind of....the pump can't go faster then the overflow or you'll have an overflow. Trigger pretty much covered everything else except I don't agree with the check valve part, Those things will fail, and it will fail when your not home. IMO, a siphone break is a much better way to stop the return siphone.
 
trigger16

trigger16

Member
True that is why you should drill a hole at the higest point of the return pipe in the tank. That way that breaks before the overflow.
 
ricker

ricker

Member
when you say highest point of return line, do you put a tee and have the whole on top of the end of the tee or is it on the 90 that goes down into the tank?
 
squidd

squidd

Active Member
On the 90 or just below near the high waterline...some water flow will come out of this hole so you want it in the tank.
 
lar

lar

Member
Guys,
Is it possible to use a pump that would return water faster then the siphon pulls water. What would your recommendation be for Max. return rate on the pump?
 
trigger16

trigger16

Member
You always want to use a pump that pump more out than comes in.
You have to install a ball valve on the return line to control water flow back to the tank to match the water coming in from the tank.
 
salty jeff

salty jeff

Member
You need to install a ball valve on the PVC pipe coming off of the return pump. That way you can adjust the return water flow so it will not out pump the overflow. They sale them where you buy your PVC pipe.
 
bigmac

bigmac

Member

Originally posted by Trigger16
You always want to use a pump that pump more out than comes in.

OK, I'm missing something on this one (not the first time) why do you want output to be faster then input?
 
squidd

squidd

Active Member
I think he means (or the correct way to state this is) :
You always want your overflow to be able to remove more (have a greater flow rate) then the return pump pumps in...
Not necessasarily "faster" (you want input and output balanced so the tank level remains stable) But you want to maintain the "ability" to remove more water than is pumped in so you never overfill the tank.
 
trigger16

trigger16

Member
Just commons sense.
If more water enters the sump than that which the pump can pump out, then you will overflow your sump rather fast.
You need a pump that can pump more out then the overflow puts in.
That is why you HAVE TO plumb a ball valve to teh return line to control th e flow rate of the pump. You cannot control the flow rate of the overflow. Somewhere you have to control it.
 
squidd

squidd

Active Member

Originally posted by Trigger16
Just commons sense.
If more water enters the sump than that which the pump can pump out, then you will overflow your sump rather fast.
You need a pump that can pump more out then the overflow puts in.
That is why you HAVE TO plumb a ball valve to teh return line to control th e flow rate of the pump. You cannot control the flow rate of the overflow. Somewhere you have to control it.
Actually this is kind of backwards...
Discounting a small amount of "backwash" you get from your tank in a power out situation (anti siphon hole in return line and a bit of extra room in sump covers this)
And discounting losses from evaporation (leave a little over the top of pump to eliminate "dry run"):
In a properly setup, matched tank/sump system your tank level and your sump level should not change much NO MATTER HOW MUCH your pump puts out or doesn't put out...
If you need to "throttle back" your return pump...Your overflow is too small (underrated)
As long as overflow is capeable of removing more water than is pumped in tank level cannot rise...Tank level is set by overflow, if level goes below overflow it stops.So tank level is "fixed"...
Sump level is also "fixed" (discounting backwash and evaporation) The overflow CANNOT "return" any more water than was pumped up to the tank...You pump 500gph up...500gph will come down...no more no less.
You do not need a ballvalve on the return line...you do not need to "control" the flow rate...In a properly setup/matched system it is "self regulating" and does not need to be controled...If you want less flow "thru" your tank (turnover) get a smaller pump.
 
lar

lar

Member
Thank-you
This is what I had a mental gap on. In a gravity feed overflow
it's absolutely self-correcting. However in my feeble brain it seems like a siphon would be a constant smaller flow rate.
 
lar

lar

Member
That puppy is big, I get it. How do you get the siphon going on that hog. What's the brand? I will check that one out.
 
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