durso flow capacity

[rufio173]

Hey guys,

I need someone with experience with a 1 1/4" durso overflow through a 1" bulkhead. How much flow do you get out of it. I know that I've heard that it can handle 600 gph, but I also know you can bump that up to 1000 gph.

Any thoughts? I know that with a siphon, you can drain water faster than through just a gravity feed, so a semi-siphon created by the durso will probably allow more water to drain. Is the key to faster draining going to be installing a ballvalve to control the amount of air input so I can get as close to a siphon without creating a full siphon which would be noisy and a PITA.

I'll be using the thin wall PVC (sch. 26).

Peace,
John H.

[j.stagner]

Richard Durso discussed this on his website, sorry I don't have the link.

From what I remember, his comment was that some people had used it as a partial siphon to increase flow with success, but that he wasn't recommending it.

I feel the same way. The overflows should be run as overflows, not as partial siphons. The chance of having problems may be low, but the results could be devastating if a problem ever occurs.

In fact, I have two Durso standpipes on my tank, even though I only need one to handle the flow. I think that redundancy and safety is important for any investment this large.

FWIW, my experience is that the Durso like you describe will handle 600gph easily, and slightly more though I don't have exact metrics. My return pump puts out around 750gph at the height of the tank, minus losses due to plumbing.

[rufio173]

Thanks J. Stagner,

I was deciding whether I wanted to use the second 3/4" bulkhead as an overflow as well, so I think I will now, but I don't know why a partial siphon should be very devastating, b/c it would be very hard to overflow since it is only a partial siphon and you still have the air bleeding out if the siphon breaks so that it wouldn't overflow.

Any others with thoughts on this situation?

Peace,
John H.

[j.stagner]

Well, here are some stories from my own experiences of not having enough additional overflow capacity on my last tank. You may never run into them.

First: I had a HOB overflow rated for 800 gph and was running a 600gph return. I upgraded to an 850gph pump that, at that head height, should have been returning around 700gph. Unfortunately for me, there were a lot of sponges and other life forms living in the overflow and it no longer supported even 700gph. Wanna guess how I discovered this?

Second: Related to the first. I replaced the first overflow with another rated for about 900gph. After some time, I once again had things living in the overflow plumbing that reduced flow and eventually caused problems.

Third: Less likely to happen, but funny... Thinking it would not be a problem because I had plenty of room left in the sump to catch the overflow, I left the return pump running when adding about 50lbs of live rock. Quickly adding that much rock and not having enough extra flow capacity overflowed the aquarium.

Of course, these problems would have been prevented with regular maintenance, but illustrate the kinds of things that can happen.

Now, I have one Durso performing main duty as the overflow to the sump. The second one is about 1/4" taller than the first, and almost never has any water flowing through it, hence nothing living in it. If the first standpipe gets clogged or anything else happens, I have another of equal capacity available.

Additionally, sometimes when I first start up the return pump and the water in the overflow section is rising, it rises a couple of inches above the top of the Durso initially. Once the Durso kicks in, the water level goes back down to normal and fluctuates slightly for a short period of time. The second standpipe really helps in this situation.

Also keep in mind that you may someday want to add a surge bucket or other surge device which creates periodic increases in your overflow rate. Dual standpipes with lots of extra capacity will very nearly be a must.

[j.stagner]

To clarify, it's not a question of the siphon emptying your tank, it's more a question of being uneasy with relying on the siphon to keep up with your return rate.

[rufio173]

J.,

Well, I guess I'm going with both as an overflow. It helps to be protected and the extra one will put my mind at ease. I'm just glad I have enough room in the overflow box for the two durso standpipes.

I don't think I'll ever add surge devices on my 60 gallon cube, but later on a much larger tank, I will probably think about it.... however, there are so many cool wavemaking devices out now... Tunze wavebox, wavemaking machine by Paul at oceansmotions!

We've got a lot more to choose from for water motion nowadays.

Peace,
John H.