Alternative pond skimmer design -- good or bad?

[djoliver1]

Hi all:
I've been considering different alternatives for a pond skimmer, since I don't have one in my pond and it badly needs one. My pond is approximately a 9 ft. by 12 ft oval made with a plastic liner. I considered just adding an internal skimmer you hang on the side of the pond, so I wouldn't have to cut through the liner or break up the rock border of the pond, which is cemented in place. But I've already got too much equipment in the pond (4100 GPH pump, hose, with a UV light tee'd off of it. If I went with an internal skimmer, I'd have to add another, smaller pump to the bottom of the pond and it would end up looking like a junk yard down there (once my new UV configuration kills the singled celled algae and makes the bottom of the pond visible again, that is.)


https://www.gardenpondforum.com/gal...-floaters-contains-the-foam-around-waterfall/

-- the pond goes 12 ft back from the waterfall towards the camera. not much of it is visible in this photo, but better than nothing. The 4100 GPH pump on the bottom of the pond pumps through a flexible hose out of the pond into a buried pipe that dumps the water at the top of the creek, to flow down into the pond again.

So here's the alternative idea I wanted to get some opinions on. Someone told me that I could just build a rock chimney around the 4100 GPH pump at the bottomof the pond. The chimney would be approximately 32 inches high to extend 4 - 6 inches below the water level. The pump would suck the water down this chimney, skimming the pond surface in the process. I could also put a screen at the top of the chimney or just below the top border of stone to catch the floating debris, which I could scoop out as often as necessary. I know of some fairly nice stone cut in 4 x 4 x 12 pieces approximately, that I could stack up around the pump. It might look ok, like a curious underwater feature the fish could swim around. It wouldn't be water tight, but presumably, it would be good enough to suck primarily from the top, since that would be the path of least resistance. I'd put a couple layers of garden cloth between the bottom layer of stone and the plastic liner to protect the plastic. I think that with a 4100 pump in a pond that has only about 120 sq ft. of surface area, I should be a pretty good flow and circulation of surface water.

Does anyone have any experience with this chimney type skimmer design?

Does anyone see any problems right off the bat having that much stone in the pond?

Any suggestions what else I might use to construct this type of skimmer?

Any warnings before I attempt this experiment...

Thanks in advance for your input...

djo

 

[Waterbug]

A skimmer works by breaking surface tension. It's surface tension that pulls in floating stuff, not current. Having the top of the chimney 4-6" below the water surface would have no effect on floating stuff.

This type of deal can work as a skimmer. It would most often be called an overflow. In a single pond an overflow doesn't work. You need at least 2 ponds and the overflow can only be used in the higher pond. The pump is placed in the lower pond and pumps water into the upper which overflows into the skimmer and down to the lower pond.

But normally this all is done with a stream rather than a chimney. A skimmer basket is placed at the end or head of the stream.

DIY skimmer

If you're doing this just to remove foam you may be disappointed. A skimmer will reduce but not eliminate foam. It all depends on what level of foam you'd be OK with. However I do think skimmers are probably the best thing to add to a pond after water and fish.

 

[brandonsdad02]

I have found out that over feeding the fish can cause foam. I had that problem last year with my pond. I was feeding the fish when I got off of work, but my wife had been feeding them too during the day. I didn't know so we were over feeding them. Your best bet would be to find a place where you could cut the liner and place a skimmer box. Waterbug has a nice design for a DIY skimmer box.

 

[djoliver1]

Good to hear from you again DJO, alias waterbug. So are you saying that 6 inches below the surface is too far down for an overflow (chimney) to work as a skimmer?

I read your article about how to create a DIY skimmer box already, which I thought was very cool. But at this point, I'm not sure I could do something like that, since my pond is already built. I think I would have to use a prefab skimmer box with a wier that I could glue and bolt the liner to, before cutting out the opening. I'm considering going that route vs. just hanging a smaller skimmer box on the side of the pond.

But it sounds like you don't think the chimney style skimmer would be the best way to go at this point.

BTW, the hemp rope solution around the waterfall has my foam contained for now. It's a tolerable solution until the water quality improves and foam goes away naturally.

I've corrected the UV arrangement so that it tees off of the main line from the 4100 pump. At first I partially closed the ball valve to 50%, which I assumed allowed 1000 GPH through the UV filter and pushed 3000 GPH through the main line. After 60 hrs, I didn't see much change, so I opened the ball valve full, which I presume is now pushing 2000 GPH through the UV. (UV supports up to 3000 GPH for clarifying water) I'll give that a couple days and see if the water clears up noticeably. If that doesn't do it, I guess I'll change 30% to 50% of the water.

Thanks again,
djo

 

[Mucky_Waters]

The hardest part about a DIY skimmer is getting the floating weir portion of the skimmer to work properly. A properly designed skimmer will have a self levelling weir that basically floats right at the water surface level, and is able to make adjustments for a certain amount of fluctuation in the water level. It sounds simple enough, but from experience it can be tough (and time consuming) to build a DIY one that works anywhere near as well as a manufactured one. You could spend days fooling around trying to get your rock tower idea to work, and you might be half successful if you can keep your pond water level exactly the same all the time, but in the real world with water loss through evaporation and water gain from rain, it can be rather difficult unless you have some elaborate automatic water levelling equipment installed in your pond.

For these reason I would suggest you bite the bullet and just purchase a manufactured skimmer and figure out how to install and plumb it into your pond, that alone may take more time and effort than you think.

If you can figure out how to connect it to your existing pump then you won’t need to buy another dedicated pump, but don’t know what you have exactly for a pump. Does it have a provision for a pipe inlet? What have you got down there? Pictures?

 

[djoliver1]

This is getting pretty esoteric. You both seem to have answered a question I was going to ask about whether a weir door is necessary for a skimmer to work. I assumed it wasn't, because the current from the suction of the pump would pull everything into the skimmer box and that same suction would keep it from flowing back out again.

Waterbug seemed to stress the good luck of his DIY weir door design and just clarified that it is not the current that pulls the surface debris towards the pump, but rather the manipulation of surface tension by the door, I presume. I assume that is what Mucky Waters is talking about when referencing to the floating weir portion, that is, the door, correct? Or do I misunderstand?

Waterbug also seems to prefer everything to be single function and dedicated to doing the one job it was designed for. so I assume he would advocate for a dedicated pump for the skimmer and another for the waterfall and filter, etc. Is that how you design your ponds Waterbug?

My pump is a 4100 Alpine Hurricane, Mucky. It doesn't have an intake you can attach a hose to. It's about 12 " long and 11 " in diameter. If I were to build a skimmer box into the side wall of the pond, and I guess I will, I think I'd have to get a box that could hold and handle that pump. The Atlantic Skimmer and the Laguna Skimmer both seem big enough to do that -- the Atlantic skimmer box provides some mechanical filtration as well. The pump would sit in the skimmer box and suck water in through a big enough weir opening to handle the pump (9 " ). From the pump, I'd then probably send the main line to a skippy type DIY filter at the top of the hill before dumping the water into the creek. I'd tee off of the main line into a UV filter at the top of the hill which would dump into the creek without going through the skippy filter.

Does that design sound ok?

Atlantic Skimmers​

PS 4500​

Atlantic Skimmers provide mechanical filtration for outstanding water clarity. In addition to housing and hiding the pump, the advanced filtration provided by an
Atlantic Skimmer is essential for mantaining a healthy water garden.

• Super Flow weir doors for maximum surface cleaning.
• Designed to be easily camouflaged with natural materials and plants.
• Rugged high-molecular weight polyethylene shell warranted for life.
• Each unit included removable lid, filter mat, basket and silicone.

Here's the Alpine Hurricane 4100

Item# Model Watts GPH Max Head GPH @ 5' GPH @ 10' GPH @ 11' GPH @ 13' GPH @ 16' Outlet

22263 PAB4100 350 4100 23' 2749 1923 1728 1534 901 1 1/2

 

[Waterbug]

So are you saying that 6 inches below the surface is too far down for an overflow (chimney) to work as a skimmer?

Yes. I'd go a bit futher...it won't work at any depth. I didn't invent physics, I'm just the messenger.

But at this point, I'm not sure I could do something like that, since my pond is already built. I think I would have to use a prefab skimmer box with a wier that I could glue and bolt the liner to, before cutting out the opening. I'm considering going that route vs. just hanging a smaller skimmer box on the side of the pond.

Prefab boxes are fine. Installation is no picnic and adding to one to an existing pond takes even more skill. I suggest hiring someone...someone who knows what they're doing and stands by their work. That excludes the original builders imo.

Getting the elevation of a skimmer (prefab or DIY) is important. Even pros mess it up. Just read a thread in another forum where builders having to move a skimmer in a $100k gunite pond. You don't have a lot of play, much less than the height of the door. Normally it's not the end of the world. Too low the pond just looks low, silly loss of volume. Too high and the pond overflows a side which hopefully is easy to fix if there's extra liner.

Making the chimney work.
My DIY skimmer can be built into the chimney. Top of chimney about 4" above the waterline with a rectangular opening down about 8" or 10" and as wide as you like (6,810,12"). Cut the corrugated plastic weir and press into place. The flap part is cut a bit narrow so it doesn't rub the sides, while the bottom piece is a bit too wide and binds on the wall to stay in place.

To get the right height on the chimney run a string across the pond and measure down to the water surface to get a reference before the water is lowered. I would do this even if you hire someone in order to check their work. A pro won't mind. In fact they'll be proud of getting it dead on.

You'd also need a skimmer basket. I'd find what ever you like, lots of cheap plastic baskets at the dollar store. Buy the basket first and build the chimney to fit the basket.

Done.

Options
The 8" tall opening gives you 4" of water level either way. Making a taller opening gives more play, as much as you like. You just have to make sure there's enough room in the box for the door to lay down completely. So a 8" tall door requires say at least a 10" wide basket.

One reason I like the DIY skimmer is because it's easy to move the door up and down after the pond is filled. If I make a mistake it's a 30 minute fix and almost zero cost. With a box you have to patch the liner and then, because of the new seam, the box has to be moved. About a full day work, lots of adult language.

If you ever do want to give it a try I can post more detailed instructions as needed. IMO it's easier than a prefab, but I understand to someone who has never done it before, the prefab looks easy. Perform ponds have the same issue.

Mucky, the corrugated plastic weir is butt simple. Cut it out with scissors, score one side, press it into place. Takes about 5 minutes. Material is free.

Waterbug also seems to prefer everything to be single function and dedicated to doing the one job it was designed for. so I assume he would advocate for a dedicated pump for the skimmer and another for the waterfall and filter, etc. Is that how you design your ponds Waterbug?

My preferences in order:
1. Things that work. Not kind of sorta, sometimes, maybe.
2. Simple rather complex just for the sake of being complex.
3. Less money and time rather than more money and time. Many times the easier solution is cheaper. It's just the more expensive things have better marketing.

I would never have more than one pump in a water garden. My San Jose ponds had 6 connected ponds, 2 streams, 3 waterfalls, 2 skimmers, a bog and various filters at different times using a single 42 watt pump. Koi ponds are a different matter. Skimmer and bottom drains really require at least 2 pumps. One can be used but it's tricky and error prone. Plus those ponds generally really need 2 pumps anyways as back up because their fish load may require pumps to keep fish alive.

 

[Waterbug]

Here's another idea you'll think strange...this chimney thing...I'd build the falls catch basin and integrate the skimmer into that. But that's me.

 

[Mucky_Waters]

Here's another idea you'll think strange...this chimney thing...I'd build the falls catch basin and integrate the skimmer into that. But that's me.

Waterbug that waterfall catch basin looks like it would work well for capturing all the waterfall foam, the only thing I see deficient with it is you are left with nothing to skim the water on the main part of the pond (leaves, dust pollen, etc...)

DJO you got lots of options before you, sounds like Waterbug is willing to help you build a DIY skimmer, might be worth taking him up on it. If I was to built a chimney thing with skimmer ( prefab or DIY), I'd do it at the far side of the pond from the waterfall to get the best water circulation across the pond and have the skimmer basket within easy reach for cleaning.

 

[djoliver1]

Thanks for your input guys and your offer of more detailed information, Waterbug. Integrating the skimmer into the falls catch basin means, in my case, tearing up the last part of my creek to make room for the catch basin before the pond, I assume. Integrating the weir would mean putting the weir door into the side of the catch basin neighboring the pond. The pump would be inside the catch basin then. It's an interesting idea, assuming that's what you meant.

But I hope to build some filtering into this pond without major surgery, if I can. I heard what you said about the difficulties of getting the weir opening at the right height with a prefab skimmer cut into the lining of the pond. If I was going to attempt to do that though, how would I go about it? Right now I have a pond full of water. So I could draw a line on the plastic liner at water level. Then I'd dig a hole behind the plastic liner down to the level where the weir opening should be. Let's assume the weir opening is 6 inches high and 9 inches wide. How high above the waterline should the top of the weir opening be? 2 inches above the water line and 4 inches below? That's my guess, but what would you do?

Once I got the skimmer box situated behind the liner, I'd have to take a foot of water out of the pond to able to do the installation, right? I'd hope that removing a foot of water wouldn't cause the liner to move, so I could just install the outer frame on the pond side of the plastic liner using silicone calk, cut the liner to remove it from the weir door opening, give it some time to set before refilling it with water, place the pump in the skimmer box and be done. What do you think of this approach?

BTW, I can start to see the bottom of my pond again, so the UV must be working now. It's a junk yard down there with pump, hose snaking across the pond, ball valve and UV light. Ridiculous mess. I'm determined to get all that crap out of the pond. I've also noticed that the water is full of particles. I don't know if it's dead algae or what, but I desperately need a mechanical filter. The Atlantic Skimmer box I pasted an image of in my last message has a slot just behind the weir door going across the box to hold a filter. It's probably for one of those 1.5 inch thick bio-filters, but I think I'd like to put a mechanical filter there to trap and capture some of this particulate matter in the pond. What do you think of this idea? Would it slow down the water too much and burden the pump? I'm just thinking of using some of that blue sheet filter material they sell at Home Depot. I'm very willing to clean that filter out every night until I get the pond cleaned up.

Thanks again for staying with this conversation you guys! I've learned a lot, since I started with no idea at all -- didn't even know what a skimmer box was.

 

[Waterbug]

...the only thing I see deficient with it is you are left with nothing to skim the water on the main part of the pond (leaves, dust pollen, etc...)

Build a regular skimmer into the catch basin, including a skimmer box. I hadn't thought of this before the chimney idea, but now I think that's how I'll do my next pond. It wouldn't work any better than a regular skimmer but I think it would be cool. Everyone knows you can't have a skimmer at the base of a falls so this would be strange...I like different.

Normally a skimmer would be away from falls because the falls messes up the surface tension. Most people do think it has something to do with current from the falls but this isn't true. If you put some food coloring into the falls you'll see that water goes down, not across.

 

[Waterbug]

DJ, first off I do want to make it clear I'm not trying to convince you of anything, I'm just talking...thinking about my next pond.

Integrating the skimmer into the falls catch basin means, in my case, tearing up the last part of my creek to make room for the catch basin before the pond, I assume.

My thinking was you were prepared to build a chimney and that's basically the same as a catch basin. In previous discussions it didn't sound like you wanted to empty the pond to build something and I assumed a chimney would require that...so my thinking is why not build a catch basin inside the pond under the current water falls. Same shape as the rope, but not as much area. I was just guessing...not really sure how you planned on building the chimney.

...getting the weir opening at the right height with a prefab skimmer cut into the lining of the pond. If I was going to attempt to do that though, how would I go about it?

Like I said earlier:

To get the right height on the chimney run a string across the pond and measure down to the water surface to get a reference before the water is lowered. I would do this even if you hire someone in order to check their work. A pro won't mind. In fact they'll be proud of getting it dead on.

I'd assume marking the liner would screw you up because the chances of the liner returning to the same place is close to nil.

How high above the waterline should the top of the weir opening be?

The manufacturer should tell you. Could even be a mark on the door. Generally I go for half way up the door. That just gives me the most play either way. Just as likely to set it too high as too low.

Once I got the skimmer box situated behind the liner, I'd have to take a foot of water out of the pond to able to do the installation, right?

I think the water has to be drawn down before the hole is dug. Water pressure will push the liner right into the hole otherwise.

...give it some time to set before refilling it with water

Here's where problems can start. When building a pond I know exactly what's going on. I know the soil I set the skimmer on is undisturbed soil and there would be no settling later. If the soil did get disturbed I'd know to compact it properly (not easy). In a retro fit I don't know the sub soil condition. So, does one wing it and hope nothing bad happens in 2 years? I think that would be the most common case. I don't like problems if the fix is easy. What I'd do is dig a wider hole parallel with the liner and a bit further away from the liner and deeper than needed. I would compact the floor soil as best I could. Then I'd pour a minimum 4" thick concrete pad, steel reinforced. You can determine the floor height using the string.

I have no idea if this would be needed or how big the pad should be. My guess would be 36" wide by 24" and 4" thick, that's four 80 lb bags of concrete. A pad is certainly not needed in new construction but in this case I'd spend the extra $30 and hour of time. Setup time of 24 hours would be OK in this case.

On the other hand it's not that hard to reset a skimmer.

BTW, I can start to see the bottom of my pond again, so the UV must be working now.

How cool is that? I always giggle like a little girl when I can see the bottom. Whether the UV did it or bacteria or string algae is impossible to tell of course. But I'd guess it was the UV. Don't assume your latest valve setting is the correct flow for future reference. It takes a while for dead algae to lose the green. So the killing may have been from an earlier setting. I'd certainly stay with the current setting, but if green water ever came back I'd consider going back to a previous setting.

It's a junk yard down there with pump, hose snaking across the pond, ball valve and UV light. Ridiculous mess. I'm determined to get all that crap out of the pond.

I agree 100%. What's the point of building a natural pond and seeing that stuff? I don't even like bare liner because there are always folds which why I rock over the liner.

I've also noticed that the water is full of particles. I don't know if it's dead algae or what, but I desperately need a mechanical filter.

I'm not sure on the time line...algae clumps (called colonies) after awhile to the point of being visible. But I'd assume the suspended stuff is all kinds of decomposing stuff. The first step in clear water is getting big stuff (leaves, fish poo, etc) out of the pond before it decomposes. The decomposition also increases DOCs which cause the foam.

I assume the pond builder talked you before hand about how to keep the pond clean? Bottom drain? Vacuuming? Oh, that's right, this guy didn't even put in a skimmer.

...1.5 inch thick bio-filters, but I think I'd like to put a mechanical filter there to trap and capture some of this particulate matter in the pond. What do you think of this idea?

When I build a fabric filter it's pretty big, like 10' long and about 1' square. The trick to fabric filters is low flow and matching the fabric to the type of suspended stuff. Unfortunately its impossible to describe. I'll say this, I've seen the amount of material removed from water to make it clear and it's an unbelievably large amount. If you could find a material that trapped your particles, for that size, it would have to be cleaned every hour and I'd it would take maybe 300 or 400 cleanings. Just a guess, but I'd be taking all bets.

But given the high water flow you'd have to use a material like in a water purifier. There are 2 basic fabric filters. Those like the water purifiers have tiny openings and don't allow anything larger to pass. OK for basically clean water, but for pond water these clog in minutes or even seconds. The second type has large openings compared to the particles. I've posted some pictures before of fabric under a microscope. These fabrics slowly clog, catching larger particles first making holes smaller which catch smaller and smaller particles. So they catch a huge amount of stuff. That's why the fabric has to be matched to the particles. Too open a fabric with water holding only tiny particles and nothing is trapped.

 

[Waterbug]

Would it slow down the water too much and burden the pump?

Only if it worked. The pump could burn out.

I'm just thinking of using some of that blue sheet filter material they sell at Home Depot.

Link? I would assume it would be far, far too open.

The first time I ever heard of fabric filters working was many years a go and they were using panty hose. It didn't work for other people but it did start me on the fabric filter path. I couldn't get the panty hose thing to ever work. The material I end up with was more like a tee shirt (but I didn't get a tee shirt to work) and was a polyester. Under the microscope the fibers have little hooks, or thorns, on them which I think may help start the trapping process.

I'm very willing to clean that filter out every night until I get the pond cleaned up.

That's the sign that a fabric filter is working. If it doesn't clog in a day or two it won't in a week or two.

Daily cleaning is what I shoot for in sizing a filter and also so the pond is clear in a few days.

 

[djoliver1]

Thanks for all the feedback and advice, Waterbug. I do know that the place I'm thinking of putting the skimmer box is good hard Georgia clay that hasn't been disturbed. Now I've just got to get the box and try to install it.