How does a skimmer work?

[Samuel]

https://www.gardenpondforum.com/gallery/image/2171-iphone4s-053/


Well this is a crude drawing of what i got going on right now. My pond was never really plumbed correctly, and have never had a drain of any sort. There has been a 2' pvc end just hanging out at the bottom letting water in and up to the filter. I got the Idea for a Drain based off the above liner 2'' tetra vaccum drain, i hope you know what i am talking about because i just learned about it this morning. I have here a second drawing however of an idea for a skimmer of some sort but am not sure if this is how it is supposed to be plumbed either. I live in Vegas and my water level in the summer can drop inches in a very short period of time. sometimes inches. I saw a few videos of people with some skimmers that i like. Looked to be an end of pvc pipe just below the surface of the water causing water to be drawn toward the skimmer. Based on this can the pvc pipe breach the surface of the water and just have slits in the sides? This way water still flows down inside it but with longer slits it would accomidate different water levels. Any ways i wasnt sure how the plumbing works. Can the skimmer be t'ed into the line going toward the filter?

https://www.gardenpondforum.com/gallery/image/2170-iphone4s-054/

 

[buckry]

No that won't work, you've got to have a door that moves with the surface of the water. The door maintains a constant surface tension that keeps stuff flowing in. It's a mini waterfall inside the skimmer box, the pump just keeps taking water away and the skimmer door lets if fall in with debris. The door's mini waterfall won't allow any debris to slip back out. You slit method is probably just going to suck air and some water into it, it may or may not get a leaf or two, probably just up to random luck. Plus slits is only going to let small debris in, leaves or pellet food or sticks will get stuck on the outside requiring manual removal.

 

[Samuel]

Ok buckry. That being said I have seen slimmer boxes. Is there a basic drawing or something that shows how it's plumbed. It's hard for me to wrap my head around things I don't understand. I just have the one pump. Not sure if that's all I need with a work over with e the plumbing.

 

[buckry]

Plumbing it is easy, it's a box that fills with water, the pump just sucks water out of that box. I can't think of any alternate ways to plumb it, in my case my pump sits on the floor of the pond and sucks the water straight down out of the skimmer. I simply jet the water across my pond, but I could easily send the water to any number of other devices instead, a bio filter or a waterfall would be easy to connect to, I just want it to make a nice current though so that works out perfect for me.

If it's a powerful pump it can probably be used for a whole variety of things, just depends on the pump.

 

[Waterbug]

The skimmer you're thinking of is called a no niche skimmer, because there's no niche in the side of the pond. The door Buckry is talking about is on a niche skimmer, so unrelated to the kind of skimmer you're going for in the picture.

The principle Buckry is referring to is however the same, just no door. A no niche skimmer floats, or a section of it floats, so the openings is just below the surface. Being just below the surface pulls surface tension like Buckry was saying. Google "no niche skimmer" if you want more info. Google "diy no niche skimmer" for some cool ideas.

I think I may know the DIY skimmer that may have inspired you, looked like the top of a castle turret. I'm not sure why they had the slots, maybe to keep fish out. Do you have the link to it? But you definitely can't have slots running below water because that just draws in water below the surface.

So the trick for a no niche is getting it to float up and down with the pond level.

A stationary skimmer can work if the pond is two pools and the pump is in the lower pool so the upper pond overflows into the lower pool. That means the pond is always a constant level. These skimmers are super simple to make, just an overflow pipe.

There is also an issue trying to run a bottom drain and skimmer off of one pump. Tricky.

Is a nich skimmer possible? Here's mine DIY skimmer.

 

[Samuel]

Waterbug that's not exactly the one I was looking at but pretty much the same thing. It looks stationary. What happens with it if the water level was to drop? And how and where is that water being pulled to?
My biggest concern is that I don't have a bottom drain. In my head a skimmer of what ever sort would have to be plumbed down low in the pond. Connected to the one supply line feeding the pump. So there would be suction at the drain that I'm putting in,and suction at the skimmer. The drain is just going to rest at the bottom facing down. Like a vacuum. I do t think I can run the line from the drain up and out of the pond and back down into a nich skimmer. Is this making since or am I completely off from how it works?
My pump and filter work great as far as water clarity goes but as it is right now the end of PVC supplying the pump sits about a foot above the bottom allowing heavier sedement to settle below it on the bottom. It has never had a skimmer and am trying to just figure out what I need and how to do it. I appreciate your guys patience.

 

[Waterbug]

I understand the type of bottom drain you're thinking about, it's generally called a "retro fit bottom drain".

Your scheme of connecting both the bottom drain and skimmer to the same pump sounds good in theory.. Problems appear when you try to use it. The water doesn't know you want both devices to pull equal or useful amounts of water. Instead one will pull more than the other. So you end up with one device hardly working. To fix that you can add 2 ball valves to control the flow on each device. The cost of those ball valves is about the same as a new pump. Also, with one valve closed a bit there's a pinch point inside the pipe where leaves and such can get stuck causing clogs.

So I'm going put a stick in the mud and say you have to have 2 pumps. One for the skimmer and another for the bottom drain. Running one pump to both is too complex and rarely works. If you want to try, super. But I can't really help. Just too complex to discuss in a forum.

What happens with it if the water level was to drop?

A proper skimmer would stop working. In your drawing, because of the vertical slots, the skimmer would continue to draw water but it would not act as a skimmer. That design isn't a skimmer because 99% of water drawn in is always going to be subsurface.

Bottom drain pipe size...
A 2" pipe on the Tetra vacuum drain is undersize imo. This is very common from mass market manufacturers like Tetra. Their primary job is to sell you on something, not on whether it works. Most people only run a pond for a year or two before giving up. That's Tera's market. No experience, no desire to research, just people standing in front of a display at a big box store making an impulse buy. Not their fault, buyers demand cheap, easy sounding stuff over functional. A 3" line would be much more expensive, bulky, and more intimidating to novice pond keepers.

The issue is clogging. Leaves, sticks, string algae is much more likely to clog a 2" line. When you have these issues, and you likely will, and the 2" line is clogging every few minutes you will shut it down and that will be that. A 4" line would be the standard for a bottom drain, but 3" is also often used.

TPRs (Tangential Pond Returns)...
You can Google these. A bottom drain by itself is fairly worthless. It will only suck up debris within about a 2-6" radius around the drain. The drain is only one part of a 3 part bottom cleaning system. One is a filter to remove the stuff collected, like the bead filter you have in your drawing. One is the drain. The last is TPRs which create a rotating current in the pond to sweep debris to the drain.

Summary
A generic type system would have 2 pumps, one for the skimmer, one for the bottom drain. The skimmer can have a basket to collect waste, the bottom drain goes to a filter. The best filter for a bottom drain is a gravity fed sieve. May people do use a bead filter but these need to be back washed often, and are expensive in electric cost and water loss from flushing.

The skimmer plump output is generally sent to the the TRPs. The bottom drain output generally goes to additional filters and then back to the pond thru some water feature like a falls and/or stream.