Pond sieve confusion.

[Peppy]

I guess there are only two, the Aqua Forte (Ultra Sieves) and the Cetus.

So here's the problem:

Cetus: 4700 gph
Ultra Sieve Midi: 3300 gph
Ultra Sieve III: 7900 gph

These numbers aren't working for me. My BD is 5500 gph. I hate to buy the most expensive of the three, the Ultra Sieve III, because I feel like it's overkill for a 5500 gph BD but it's still not enough for the BD and skimmer.

I'm afraid if I downsize to a 4700 gph BD pump for the Cetus, the system won't work. It works now but I feel any small change might screw that up.

I've often though I should have 2 bottom drains but I slanted everything toward the middle.

[Meganne]

you got it Peppy, it is asystem and it all needs to work together .
the flow of the BD is good as you want to make sure it can get enough to the system, so I would think it being close to what a sive could handle would be good. I would be looking at what flow rate your filters and settling chamber can handle. these are the areas that can be drawn down to far or ovr flow .

anyway that is what I am thinking, hope someone reins me back in line if I am off!

[Birdman]

The Cetus Sieve is installed right will give you 5000 gph flow. I would think that would be close enough to your target of 5500 gph.

[koikeepr]

How are you arriving at that 5400 flow rate number? The generally accepted figures based on pipe size is as follows:

1-1/2" = 350 gph
2" = 750 gph
3" = 1500 gph
4" = 3000 gph

[Peppy]

Uh oh. So you're saying a gravity fed 4" pipe maximum flow is 3000 gph, koikeepr? Then I'm screwed. The whole system would have to be reworked. I can't believe a piddley 3000 gph retro BD would clean my pond bottom. The pond is approx 16' x 20' so take away 3 shelves at probably 12" each (guessing) that makes a 10' x 14' bottom or 5' minimum 7' maximum radius around the retro BD.

Birdman, will a 3000 gph BD clean a 7' radius?

I'm probably looking at a new pump anyway since mine is probably frozen. Long story.

[WeWilly]

You don't have enough BD's for that size pond

[koikeepr]

Bill beat me to the punch here, but he is correct.

I have a 10x20 pond and I have two 3" drains. Your distance is very long and I think you'd be better served by two drains spaced properly apart rather than one. WeWilly has some great deals on some drains you should check out in the trader forum. I got one for a friend who I'm helping build a pond for, and it was great. They are 4" drains, but I just necked it down to 3" without dilemma. My two 3" drains feed directly into my midi sieve with no problem at all.

[Ponderer]

How are you arriving at that 5400 flow rate number? The generally accepted figures based on pipe size is as follows:

1-1/2" = 350 gph
2" = 750 gph
3" = 1500 gph
4" = 3000 gph

I have a 2" pvc bypass pipe 16' long diverting from my waterfall directly to my pond the first 6' is at a 45 degree angle from top of my barrel filter the remaining 10' 90 degree elbows off the 6' and is parallel to the ground. The pump is 2900 gph with only 4' of head, the 2" pipe handles it well.

[Peppy]

I do need 2 bottom drains if I can't have 5500 gph. I didn't realize that gravity feed would limit my gph.

I think the reason my BD works is that it's 5500 gph and the floor is only 10' x 14' so the maximum radius is 7'.

There is a circular flow that sweeps the shelves clean and once the stuff hits the floor it only has 7' to get to the drain.

But if I switch to gravity feed and am limited to 4000 gph...well, what you said, WeWilly.

I angled the bottom toward the middle. Will 2 BDs work with a dip in the floor between them?

[koikeepr]

Help us understand this statement:


I think the reason my BD works is that it's 5500 gph and the floor is only 10' x 14' so the maximum radius is 7'.

What makes you say your BD is running 5500gph through it? Is it because you have it connected to a 5500gph pump? This is not the only factor--what is the pipe width that the BD is connected to?

A decent radius for a BD is normally about the radius footage you are mentioning. Again, a particular diameter pipe can only flow so much based on it's width size. Every inch you add to the pipe ends up about doubling the gph that can flow through it.

[Meganne]

gravity flow does not limit your flow, pipe size and what your filtration system and how much water your pumps pull does.
with enough flow and the bowl of your pond I would think you could keep the floor "fairly" clean... how has it been?

[Birdman]

Uh oh. So you're saying a gravity fed 4" pipe maximum flow is 3000 gph, koikeepr? Then I'm screwed. The whole system would have to be reworked. I can't believe a piddley 3000 gph retro BD would clean my pond bottom. The pond is approx 16' x 20' so take away 3 shelves at probably 12" each (guessing) that makes a 10' x 14' bottom or 5' minimum 7' maximum radius around the retro BD.

Birdman, will a 3000 gph BD clean a 7' radius?

I'm probably looking at a new pump anyway since mine is probably frozen. Long story.

The general rule of thumb is a 4" BD needs a min.of 2500 gph to keep the 4" line swept clean. But they can flow much more, just depends on the drop. In my 6700 gallon pond I have two 4" BDs, each is going to one Cetus Sieve. I am getting close to 5000 gph through eace 4" BD Sieve combination.

EA, the maker of the Cetus Sieve states 4800 US GPH when the sieve is installed at their recommended height. I installed mine 1" lower than specs. which gives me the additional flow.

General rule of thumb, a 4" BD will sweep a 6 foot radius @ 3500 gph. Increase the flow, more sweep,dish the floor,more sweep, add more fish, more sweep, as the fish movement does allot to help sweep the bottom.

All things considered, If I was building a 20 by 16 foot pond I would go with two 4" BDs.

Here is a picture of one of my Cetus Sieves flowing 5000 gph. There is 1/4 inch of travel left in the weir.

[Peppy]

Okay, wow, memory is worse than I thought. Had to get out my pond redo pictures to see just how many shelves I have and it's 2, not 3. Hard to believe I could forget something like that but oh well.

So that makes the largest radius around 8' and not 7'.

So this is a cut-away of the pond (not to scale) -- lengthwise--the longest part that is 20'. These are approximate because I keep forgetting exact figures but it's around 16' x 20' and the shelves are around 1' wide.

[Peppy]

Koikeepr, yes, I'm only stating the pump size because I don't know the actual flow and I'm using 3" pipe up and over the side wall to a 5500 gph pump so it's probably more like 4500 gph when it's all said and done.

So in the spring, I want to change to 4" pipe below the water surface.

Right now, the bottom stays clean which amazes me. At the bottom of the set of steps I built into the pond is where debris does still settle but it's not a lot.

Here's a top view (without the steps for walking in and out):

[Peppy]

So the BD only has to sweep the 8' x 6' area. The circular flow keeps the shelves clean. I see stuff on the shelves likes seeds and things but they eventually make their way to the bottom which is nice.

That's why I don't want to mess with the flow because it's working with the present gph. If I decrease that, who knows what will happen.

So if I could have a cetus on the 5500 gph pump using 4" pipe, I hope it would work the same.

I also think, so help! here please, that since I'm going into a pressure filter, that must further reduce the flow.

So could I hook up a cetus to the 5500 gph pump and pressure filter with a ball valve and then if the flow is too much torque it down using the ball valve?

And all this if my pump is actually still working since I couldn't get to it under the greenhouse and it could be frozen solid and broken.:sad0049:

[Birdman]

That's why I don't want to mess with the flow because it's working with the present gph. If I decrease that, who knows what will happen.

So if I could have a cetus on the 5500 gph pump using 4" pipe, I hope it would work the same.

I also think, so help! here please, that since I'm going into a pressure filter, that must further reduce the flow.

So could I hook up a cetus to the 5500 gph pump and pressure filter with a ball valve and then if the flow is too much torque it down using the ball valve?

:sad0049:

What your saying is correct, but it might not work.

Where is the pipe from your retro drain going? Up over the side of the pond? or through the liner in the wall of the pond.
To work with the Cetus Sieve the 4" BD pipe can not go up over the pond top edge then back down to the Cetus. That will trap air and not flow water.

The 4" BD pipe has to stay horizontal from the BD to the Cetus inlet. It can go up, but can not go up then back down. The inlet of a Cetus Sieve is 3 feet below pond water level, your pond is 4 feet deep, so your BD pipe would run up hill from 4 feet to 3 feet.

Another thing the ES 5500 pump is not designed to buck very much pressure. Depending on what kind of a pressure filter you use the 5500 might not be big enough. What kind of pressure filter are you thinking of?

[Lilylady]

Peppy, if it is any help to you, my koi pond is 12 X 25 and 2 bottom drains do a very good job.

[Peppy]

Sorry, Birdman, took a break from the PC for holiday.

Oh my. This sounds more complicated than I thought.

Right now the pipe is up over the edge but I SWEAR I'm going to remedy that this spring. I've done a few small pipe boots and feel pretty confident about them at this point and ready to proceed with a below-water level BD pipe going through the side of the pond.

My pressure filter is an Ultima II 4000 and is supposed to have at least 4000 gph but they said 5500 is fine.

I would not mind 2 BDs but I sloped the bottom of the pond floor toward the middle so I don't know if that will mess things up. Would it work to put a BD on either side of the 'pit' in the middle? I'm afraid stuff will settle in that pit instead of going in the BDs.

[Birdman]

I assume your not lifting the liner, but using a retro drain on top of the liner, then going through the side with a pipe boot?
If that's the case, and your pond is slopped to the center then just do one BD.
But remember, The pipe from the BD to the sieve cam only go up. It can not go up then back down. That would trap air and not flow.

[Peppy]

I assume your not lifting the liner, but using a retro drain on top of the liner, then going through the side with a pipe boot?

Yes, that's right. It's good news to hear one BD because I don't want to lift the liner and reshape the bottom because I have nowhere to put the fish.

Got it on the up and not down spec. It works now because it's a closed system into the pressure filter but I do see that it won't work going into a sieve.

And now I have to start saving my money for a sieve since I blew my bonus on collectibles. Damn. No control.