Silent and Failsafe Overflow System

[gpwdr]

I tried to read the entire thread so maybe this is a repeat question.

My sump is in the basement, so it's about a 9' drop.

Where is the best location for the gate valve on the full siphon?

I'm thinking at the sump and make the adjustment until there are no more bubbles?

Gene

 

[mmn]

I tried to read the entire thread so maybe this is a repeat question.

My sump is in the basement, so it's about a 9' drop.

Where is the best location for the gate valve on the full siphon?

I'm thinking at the sump and make the adjustment until there are no more bubbles?

Gene

I use this valve to adjust the water level in the overflow, so I have to be able to see it.

 

[uncleof6]

I tried to read the entire thread so maybe this is a repeat question.

My sump is in the basement, so it's about a 9' drop.

Where is the best location for the gate valve on the full siphon?

I'm thinking at the sump and make the adjustment until there are no more bubbles?

Gene

You will want the valve as close to the sump as you can get it. If you place it up high, you will most likely gets some cavitation as the water pressure rises, and then falls suddenly as the water passes the valve. This will create some rather annoying noise usually.

This will make it rather hard to adjust, and the initial adjustment is to raise the water level in the overflow, till water just flows in the open channel. If you are getting bubbles through the open channel, something is not working right. Also, you do not start adjusting the valve untill the siphon kicks in, and drops the water level in the overflow.

This is rather tricky to do with the valve in the basement, with the tank on the floor above; that is one of the reasons I don't recommend dumping into a basement sump. Rarely if ever is this the only option, and it would be better to have the sump right below the tank. I have not really heard a good excuse for putting the sump in the basement either. It sounds cool, might even look cool on paper, but in practice, it really isn't.

 

[Dandaleh]

Question re larger tanks

Question re larger tanks

Hi all,
I have read this whole thread over the past few days with great interest and must say its so nice to see people like Bean Animal and uncle devote so much time in a selfless manner. I am about to install a 950 US gallon (3600litres) reef tank measuring L300cm x D120cm x H100cm (upgrading from 800gallon one) and keen to install this system as on my current system im using a durso one which i dont like for all the reasons detailed in this thread. I have looked out for info re large tanks but all i could find regarding this is advice that one should add a 2nd syphon. Would this work or should i be looking at larger diameter pipes and bulkheads or both? My return pump is an Abyss 400 which is rated 18,600litres per hour (4,900litres/hr). Any advice is much appreciated as do not want to get this wrong on such a costly glass box!

 

[uncleof6]

Hi all,
I have read this whole thread over the past few days with great interest and must say its so nice to see people like Bean Animal and uncle devote so much time in a selfless manner. I am about to install a 950 US gallon (3600litres) reef tank measuring L300cm x D120cm x H100cm (upgrading from 800gallon one) and keen to install this system as on my current system im using a durso one which i dont like for all the reasons detailed in this thread. I have looked out for info re large tanks but all i could find regarding this is advice that one should add a 2nd syphon. Would this work or should i be looking at larger diameter pipes and bulkheads or both? My return pump is an Abyss 400 which is rated 18,600litres per hour (4,900litres/hr). Any advice is much appreciated as do not want to get this wrong on such a costly glass box!

Second siphon line would just add unnecessary complexity to a rather simple drain system. For safety, you would have to double up everything. That would be more than just a waste of time and material.

I don't know why you are selling yourself short targeting half the flow you should have this tank.

A 2.5" bulkhead will flow a max-theoretical of 12,759 with a 3' drop, real world friction losses in 2.5" pipe, would reduce this a bit; a 2" bulkhead would flow ~ 8000gph, max-theoretical, so would be a bit small for this tank. My choice would be 2.5" bulkheads and 3" pipe, as well as a pump that could do 10k plus, at the total dynamic head for the system. These tanks are not hobby tanks, and using hobby logic is the wrong approach. (The same logic should be applied to smaller tanks as well.)

 

[booth2010]

Quick question, on the 2 downturned 90s inside the overflow does it matter how much space is left between the glass panel and the bottom of the 90? I think I have between 1/8 to 1/4" gap. Would this little space allow for a full siphon or should I cut the PVC a bit? Its a 40B with an almost C2C 30"Lx3.5"Dx3.75"H. (Tank is 36"x18"x16")

 

[sleepydoc]

It will allow for a full siphon, but if it is too close it will restrict flow. A narrow gap also makes it difficult to clean under the elbow and/or unscrew it from the bulkhead.

How much flow are you targeting? ⅛" is quite narrow. I would do at least ¼-½". I have ¾" beneath mine, running ~1200 gph. With a 40b you likely are significantly below that, though.

 

[Pprice01]

Well, my tank was finally delivered (over 1 month late) today, and the builder made the internal overflow C2C box shallower than spec'd. It's on the side of the tank. It's a 60x28x24 setup with the overflow on the right side. The box won't fit a standard street 90 without trimming the bottom of the fitting, so I'm now concerned about two things:

1. How much clearance do I need from the bottom of the overflow box to the bottom of the full siphon fitting for it to be able to flow the water correctly? This will determine how much of the fitting I have to cut.

2. how deep does the bottom of the full siphon need to be to avoid cavitation - sucking air from the surface?

I will be running roughly 900-1000gph and the system is setup for 1.5" drains.

Thank you. I've always appreciated everyone's assistance in this thread. Please ask any questions I didn't cover.

Paul

 

[sleepydoc]

Well, my tank was finally delivered (over 1 month late) today, and the builder made the internal overflow C2C box shallower than spec'd. It's on the side of the tank. It's a 60x28x24 setup with the overflow on the right side. The box won't fit a standard street 90 without trimming the bottom of the fitting, so I'm now concerned about two things:

1. How much clearance do I need from the bottom of the overflow box to the bottom of the full siphon fitting for it to be able to flow the water correctly? This will determine how much of the fitting I have to cut.

2. how deep does the bottom of the full siphon need to be to avoid cavitation - sucking air from the surface?

I will be running roughly 900-1000gph and the system is setup for 1.5" drains.

Thank you. I've always appreciated everyone's assistance in this thread. Please ask any questions I didn't cover.

Paul

I'm running ~1200 gph; 1.5" pipes, 1" bulkheads and 1.25" elbows in a coast to coast overflow. Approx ¾" between the bottom of the overflow and the bottom of the elbow. Water depth is 2 ¾", so about 2" from the surface to the bottom of the elbow. If the water depth drops much below 2 ¾" it starts entraining air from the surface. Not a lot; the bubbles sound like some sand or small pebbles running down the pipe, so it's not terribly noticeable, but it is there. Of course, once my skimmer is turned on, it's inaudible.

What size elbow are you using? if you can use a 1.5" elbow, the edge flow velocity will be lower and it will probably be less likely to entrain air. I don't have a good feel for when the gap between the elbow and the bottom of the overflow becomes an issue; you could try cutting it down to ½" and see how it goes. As long as you don't cement you elbows in place it's easy to take it out and trim another ¼" off.

 

[Kingfisher1980]

Nevermind. Found my answer.... Don't know how to delete my post so...

 

[booth2010]

It will allow for a full siphon, but if it is too close it will restrict flow. A narrow gap also makes it difficult to clean under the elbow and/or unscrew it from the bulkhead.

How much flow are you targeting? ⅛" is quite narrow. I would do at least ¼-½". I have ¾" beneath mine, running ~1200 gph. With a 40b you likely are significantly below that, though.

Thanks Sleepydoc, I will make them around 1/4"-1/2" and see how that is. If not enough I will raise to 1/2".

 

[tidus10]

I know this is a dumb question but i figured I would ask... I can run this system with flexible PVC tubing right? Just cut it and put in the union ball valve and bring in down into the sump as normal right?

 

[uncleof6]

I know this is a dumb question but i figured I would ask... I can run this system with flexible PVC tubing right? Just cut it and put in the union ball valve and bring in down into the sump as normal right?

With spa-flex (flexible PVC pipe) yes. With Tygon (flexible PVC tubing,) it is not a good idea. The fittings are too restrictive.

 

[tidus10]

With spa-flex (flexible PVC pipe) yes. With Tygon (flexible PVC tubing,) it is not a good idea. The fittings are too restrictive.

i was thinking this http://www.glass-holes.com/1-Ultra-Flex-PVC-Pipe-ft-FT1385.htm

 

[uncleof6]

i was thinking this http://www.glass-holes.com/1-Ultra-Flex-PVC-Pipe-ft-FT1385.htm

That is standard black flexible PVC pipe. Just a fancy name to boost sales. It should be fine.

 

[sleepydoc]

Yes. The same rules apply for flex PVC as with regular PVC. What is your goal with the flex PVC? The larger sizes are not terribly flexible, despite the name, and you may be just as well or even better off using rigid PVC with some 45° fittings.

 

[Twistofer]

Yes. The same rules apply for flex PVC as with regular PVC. What is your goal with the flex PVC? The larger sizes are not terribly flexible, despite the name, and you may be just as well or even better off using rigid PVC with some 45° fittings.

I've had good experience with the Flex PVC in that not every angle is 22.5°/45°/60°/90°. Flex PVC is rigid and doesn't flex well for really tight curves, but, on the other hand, it helps with those "almost" and "just about right" fitting situations. In the right situation, it can be very forgiving.

 

[Kingfisher1980]

Back with another question. Well actually a series of them.

I built a mock up version of what was going to be my internal box/weir. I used some scrap glass I had laying about, just so I could see exactly how big it would be. It's way too big to be in a 40b. So my first question would be; can I cut some of the street elbow off where it goes into the bulkhead? This would allow me to make the box slightly smaller.

But I instead of even doing that, I'm considering just making a much smaller internal weir 3 sides siliconed in. And then building an external box with 1/4" glass to hold all of the plumbing. I would attach it to the back of the tank with the 3 1" bulkheads I already drilled for the internal setup. I would also remove the paint around the edges of the box and apply black silicone to add more support besides just the bulkheads. I already have extra gaskets to go inside between the tank and the collet and inside the box between the box and the nut.

Does this sound feasible?

 

[sleepydoc]

Yes - many people have done external boxes with an internal weir.

Two potential problems with your design that I can think of off hand:

Ideally the pass through holes would be positioned so they are at the water level. This isn't a deal breaker.

Second - you need a minimum of one diameter between the hole edge and any adjacent hole or glass edge. If you're using 1" bulkheads that means the box needs to be at least 5.25" wide.

An alternative is to make a 5-sided box out of acrylic, have matching holes and use bulkheads with a gasket between the glass and acrylic walls to hold it in place. DO NOT try to use silicone to glue an acrylic box in place. It WILL fail.

 

[Kingfisher1980]

The box that goes on the back will be made of glass and be held in place primarily by three 1" bulkheads. The black silicone will just be added measure to keep some of the stress off of the bulkheads.

The internal box I am not so worried about how wide it is, more about how far it sticks out into the tank. I will likely end up making a very skinny, and long 3 sided box also made of glass so silicone adhesion won't be a problem. The tank is also glass.

Note: the holes I already have drilled were drilled with bean animal spacing in mind. They are below the water level, but they should be fine otherwise. I think they are 1.5" apart and 2"+ from the edges of the glass. My external box will have to be at least 10" wide to accommodate them.