Question about bottom drain and gravity and skimmer

[fergus]

Hi!

I just built a pond. I'm completely stumped on how my plumbing should flow. And I'm hoping that some people here might be able to help.

Set-up:

• The pond is raised almost entirely above ground, with retaining walls around it.
• There is a kind of "bottom drain" in one corner. That is, an open pipe with no top or valve. I know it should've been in the centre, but it's in the corner.
• I also made a skimmer box which I want to use.
• For the filter, I have a small rainwater tank that is taller than the pond line, which I had in mind to use as a settlement chamber/biofilter, and an old pre-formed pond that I had intended to use as a bog filter.
• I have two pumps: one is 5000 lph (1320 g/h) with an adjustable flow rate, the other is 4000 lph (1056 g/h) and not adjustable.
• Also have a UV clarifier to incorporate into the line somewhere.

My original thinking was to have one pump in the skimmer pushing to the sump and the other pump in the sump pushing on to the bog filter, which will be completely above the water line (overflows into the pond).

The drain and where it leads into is the big question. I wanted for it to work through gravity. Does it lead into the skimmer box? I could have it connected to one of the pumps but I really wanted the line to go through some kind of filtration before it hits the impellers.

Diagrams I have seen either have the drain leading into:

• the skimmer box (example)
• directly into the biofilter (example)
• a sieve/settlement chamber (example) - with a t-section/3-way valve allowing pump to draw from both the chamber and skimmer

Are these options all using gravity? How would I stop a settlement chamber overflowing when the pumps stop?

I'm so confused. Any help would be greatly appreciated.

 

[GBBUDD]

Welcome

I can see why you might be confused, having the main drain with a long pipe smaller then the opening and so much father away really won't have much of a draw. if the pump can draw so much more than the skimmer opening can supply then that's a different story and the need will pull from the drain pipe. the issue there is it is not pressurized and the water will come through the pipe but only as fast as the available head pressure , in other words if the pond is 10 feet deep the water

the other designs with the the skimmer and the main drain coming together in a Y fitting is missing one part of the equation and that's adding ball valves to each of the pipes this way you can regulate how much draw comes from one pipe or the other.

The second drawing with the equalizer pipe being that much larger will obviously provide that much more water making the drainpipe almost stagnant. again a ball valve can regulate how much comes from what source.

 

[GBBUDD]

Pictures help

 

[Lisak1]

Welcome to the GPF! You've definitely come to the right place. Lots of smart, friendly people here who will happily give useful advice! One of them has already chimed in!

 

[j.w]

@fergus

 

[fergus]

Hi thanks very much for the welcomes

And thanks, GGBUDD. Here are some quick photos. Unfortunately it’s been pouring rain today so I couldn’t clean up around the site and it’s pretty messy.

As you can see it’s super small but I want to give it good filtration. The line that’s draped into the rainwater tank is the line from the drain. It comes up from beneath the wall. It’s not doing anything at the moment.

I also have those two black bins there that I could use for a sump/settlement chamber.

If I could rig the Y-fitting with ball valves in each line and use one of the bins as the settlement chamber (to make it like the third diagram in the original post), would that be the way to go? The intake on the pump is much larger than the diameter of my hosing, but with two intake hoses coming together in a Y-fitting - if I make the Y and the pipe (the pipe from the Y to the pump) the same diameter as the pump intake, this should be okay, right?

Again many thanks for your help

 

[fergus]

Rough diagram. Will it work?

 

[GBBUDD]

i take it your black circles are the ball valves which is where you would want them.
one other observation is your piping if you are going to enlarge the piping to the larger size that is on the pump that is certainly the way to go reducing the pipe size limits the pump and more than likely reducing what the pump is able to do choking it out.
How ever that flex pipe your using is more commonly known as kink free. But im my vocabulary it should be called it won't be long before i fail.

One other note a bio filter and a bog are doing the same job and having the bog after all that filtering if your planning on having plants in the bog they maybe choked out from lack of nutrients.

 

[fergus]

i take it your black circles are the ball valves which is where you would want them.
one other observation is your piping if you are going to enlarge the piping to the larger size that is on the pump that is certainly the way to go reducing the pipe size limits the pump and more than likely reducing what the pump is able to do choking it out.
How ever that flex pipe your using is more commonly known as kink free. But im my vocabulary it should be called it won't be long before i fail.

One other note a bio filter and a bog are doing the same job and having the bog after all that filtering if your planning on having plants in the bog they maybe choked out from lack of nutrients.

Yes and yes. The bog is extra and I probably don't need it. I'm doing it last and I might not do it at all; we'll see how much fuel I have left in the tank after all this. Is using fertiliser tabs for the bog ok?

Thanks for the tip about the kink-free tubing (I just read a couple of threads on this forum about it as well). It's a real bummer because I've obviously already fitted the drain line which is now inaccessible unless I empty the pond. I will get flex PVC piping for the rest. I'm going to hope for the best with the drain line for now.
I wish I'd properly researched that before laying; I guess I just thought pipes are pipes.

 

[GBBUDD]

if the kink free is completely left alone you maybe ok ... rocks getting sucked in could be the straw to break the camels back. if you cut the kink free out slip in the flex pvc if you then secured the flex well so the kink is isolated and not tugged at it would be your best alternative

 

[Jhn]

Rough diagram. Will it work?

No, if I am understanding your design correctly, it won’t work you need to have one pump not two. This design will empty your biofilter tank or your pond, at some point as two pumps one pumping into a sump/tank and another returning the water even if in sync perfectly initially will never stay that way, resulting in something getting emptied of water.

If it were me I would skip the biofilter and just run your one pump that is pulling through the skimmer and bottom drain, then sediment filter, then run it directly to the bog filter, or if you already have the biofilter move it to where your bog is currently. Either way it eliminates the need for the second pump.

 

[GBBUDD]

Good catch @Jhn i missed that

 

[fergus]

Hi, so sorry I missed this. Please stay with me if you can; I'm still struggling!

Okay so I will use the rainwater tank as the sediment chamber, and then from that and the skimmer, the pump will push to the filter on the other side of the pond.
I can do this. It actually makes things way simpler.

I'm assuming that any UVC would go along the pump's output line going to the filter? The instructions do say to put it before the filter - I've seen differently on these forums, but I don't have a choice as I can't put it after the filter in my setup.

 

[GBBUDD]

YOU DEFINATELY WANT THE UV AFTER THE FILTER .... the glass as it gets dirty does less. the cleaner the water the better . it is also critical to find out what the flow rate is for your unit, push to fast and too much and it wont work at all

 

[fergus]

But I don’t see how I can possibly do that since the filter’s discharge will be a simple overflow. The UVC max pipe diameter is a size smaller than what the pump’s main line would be. And yeah - checked max flow rate - is too low for my pump so it has to go on a line with reduced flow.

The only way I can think of is to add a second outlet on the filter - additional to the main overflow - with a pipe that feeds through the UVC before it runs back into the pond via gravity. So the discharge is split in two. Less of a problem but I’d also have to add something to house the UVC over there since it‘d be on the other side.