Overflow Help

[jharding08]

So I finished my tank setup with a coast to coast overflow and three drains (siphon, open channel and emergency). All plumbing is 1".





I am using an Iwaki MD-40RXT (1344 GPH) to power the return and manifold (three 1/2" lines).


I did a water test and there were no leaks, but when I ran the pump, it would empty the sump, then the overflow channel would fill up to the emergency drain. Then the pump would stop pumping for about 5 seconds, then kick back on.

Here is the sump dimensions.



I'm thinking the pump is emptying the return chamber, but not getting the water to the return exits. I got it to the point where water was coming out of the return exits, but it was backing up at the drains.

I calculated that the pump is putting 936 gph at the returns. Is that too much for a 1" siphon and 1" open channel? How long does the siphon take to start?

I think I need to add enough water in the sump to account for all piping and for the time it takes for the siphon to start. Can I just take the caps off of the drains to get it going?

 

[uncleof6]

Not enough water in the system. Pretty simple. If your return section runs dry, before the water is draining back to the sump=not enough water. And that is before you can begin to troubleshoot your drain system, if indeed it needs trouble shooting. I will also state unequivocally: Your return section is horribly too small. You need enough volume in the return section for the system to run at least several days, without the pump running dry and burning up due to evaporative losses. That is with or without an ATO. No ifs, ands, or buts. average loss is around 2 gallons per day.

With your drop, you can expect ~1200 gph through the siphon, but the open channel is really small (1.25" would be better,) so the adjustment is going to be tricky to keep the open channel quiet. However, you have some obvious problems: The horizontal runs going under the stand. These can and often do cause starting issues, as they easily airlock (trap air).

 

[jharding08]

With your drop, you can expect ~1200 gph through the siphon, but the open channel is really small (1.25" would be better,) so the adjustment is going to be tricky to keep the open channel quiet. However, you have some obvious problems: The horizontal runs going under the stand. These can and often do cause starting issues, as they easily airlock (trap air).

When you say starting issue, you are referring to the siphon starting? Does it just take longer if there is trapped air or will it not at all? Does it also matter how far under the water level the end of the drain line is?

 

[jharding08]

So I changed the drain lines to 45 degree angles and also have the lines terminate about 2" below the water level. Hopefully this will help start the siphon easier.

 

[uncleof6]

So I changed the drain lines to 45 degree angles and also have the lines terminate about 2" below the water level. Hopefully this will help start the siphon easier.

Good start, now shorten the drainlines so they are 1" or less below the water level in the sump. Basic design criteria.

Starting issues are the siphon to not purging all the air, so the siphon does not start fully. There are a finite number of reasons (only a few) why this will happen.

 

[jharding08]

While the pump was running I took off the cap to the siphon pipe and put my hand over it and it created the siphon. I figured it was leaking since I didnt glue that down. I read that people use teflon tape on the caps, so i tried that. It still didnt start the siphon. Did the action of me opening the top, then closing it purge the air?

Would the siphon start eventually? I'm utilizing the air tube just above the water line and below the emergency, so that kicks in with a siphon when the regular siphon doesnt work

 

[uncleof6]

The cap on the siphon needs to be air tight. Tape won't do it. Best would be a threaded fitting with a threaded cap, and use non-hardening thread sealant to seal it up. Tape is not recommended for use on plastic threaded fittings, according to the pipe/fitting manufacturers. Folks that use tape on a socket fitting just are not thinking well enough...

The inlet to the air vent line, needs to be ABOVE the inlet to the dry emergency. Otherwise the open channel kicks to siphon, before there is sufficient head pressure to purge the air from the siphon.

Read the design criteria again, on the first page of bean's original thread, or on the overflow page of his website. Fix everything that does not conform to the very precise instructions in his presentations. Once that is done, the system will function as it should.

 

[picker]

why have the water fall 2" onto the socks?

with only a 1" + 1" head pressure for the socks, you might find you are changing socks frequently. (perhaps not, there are 3 of them)

with 50% of the sock head under the rim, there will be quite a turbulent flow at the top of the socks. wonder if there will be splashes that exceed your 5" top-of-sump?

does it realty matter if bubbles make it to the fuge? perhaps the trap space is better for the return section which must hold the entire weir capacity.

 

[jharding08]

I got the overflow to take the entire Iwaki MD-40RXT wide open. There is quite a bit of flow through the sump...and the Iwaki is LOUD!

I figure the flow through the sump will dimish a bit when I add on my reactors and I could also dial it back with the gate valve. Does restricting flow on the outlet of the pump with a gate valve damage the pump?