Bottom drain still possible?

[daniel95]

Have just received a new polypond and didn't realise it wasn't complete flat on the base. Would these ridges & mounds make a bottom drain not work?

I was planning to have a 4" BD but if I place it in the middle, it'd be raised 1" by that mound. Another issue is the multiple ridges which are also roughly 1" high - how much will they impact the BD from working?

EDIT: Have just remembered the BD itself isn't 4" only the pipe, so the mound will be cut out. The potential issue with the ridges remains.

[daniel95]

Or am I better off going two (or one?) 3" BD between the ridge? The pond diameter is 12ft.

[mplskoi]

Those ridges are going to prevent the water from circling well. Debris will be trapped on the floor of pond if you try use two drains and have water move in a circle. I think you need to put that drain in the middle and have water drawn in to it. There are several different products and BD styles you can play around with to find one that fits. I think a floor drain type flange mounted from below might be best here. Then put a round piece of concrete (found in the patio section of a big box building store) over it to force that water to come in from the side.

[perniciousviper]

I would mount the BD proud (ie just above the ridge height) and in the centre, and seal the 4" pipe via a flange against the plastic, then pour concrete in to give you a new pond floor - a smooth bottom, gently sloping from the edges to the BD. No need to try and make the BD/concrete interface watertight, which is good as that would be impossible!

[daniel95]

Those ridges are going to prevent the water from circling well. Debris will be trapped on the floor of pond if you try use two drains and have water move in a circle. I think you need to put that drain in the middle and have water drawn in to it. There are several different products and BD styles you can play around with to find one that fits. I think a floor drain type flange mounted from below might be best here. Then put a round piece of concrete (found in the patio section of a big box building store) over it to force that water to come in from the side.

Yep I realised once I cut the hole for the BD it'd remove the mound - so the only issue is the ridges. I can't seem to work out how to get around it as the pond is already sitting in my yard waiting for install. This is the bottom drain I'd use https://creativepumps.com.au/product...-bottom-drain/ Or would your suggestion of the floor drain work better?

I would mount the BD proud (ie just above the ridge height) and in the centre, and seal the 4" pipe via a flange against the plastic, then pour concrete in to give you a new pond floor - a smooth bottom, gently sloping from the edges to the BD. No need to try and make the BD/concrete interface watertight, which is good as that would be impossible!

I wonder if there is something I could use instead of concrete? Unfortunately concrete would make the pond very heavy for future moves. I went with a poly pond so when I move house again I can just remove it and place at a new location. But I like the idea of a 'new" floor!

[cottagefog]

Is this a gravity fed bottom drain or will this be pump sucked drain?

How big is the tank, and how deep will your pond be?

[daniel95]

Is this a gravity fed bottom drain or will this be pump sucked drain?

How big is the tank, and how deep will your pond be?

Yes gravity fed to a sieve to MB. Tank is 3.7metres (12ft) diameter and water depth will/can be 1.6-1.8 (5.2-6ft) metre.

[icu2]

Do you have underwater returns trying to create a circular motion?
If so I think the ridges would be a hindrance to that but where all the ridges are directed towards the center (BD) and
only an inch high, I don't know that they'd cause much of an issue. If the BD is aerated the rising bubbles should create
a current towards the drain.

[daniel95]

Do you have underwater returns trying to create a circular motion?
If so I think the ridges would be a hindrance to that but where all the ridges are directed towards the center (BD) and
only an inch high, I don't know that they'd cause much of an issue. If the BD is aerated the rising bubbles should create
a current towards the drain.

Thanks Steve! My current pond has 2x TPRs which create the circular current so was going to do something similar. The ridges are probably smaller than 1" (hard to measure) and slopped so I may be over thinking it. I will have to see if I can source a aerated BD, Koi supplies are very rare to find in AUS and import prices are wild due to pandemic.

[UnkleTim]

Or you could bring it back and buy something more appropriate

[daniel95]

Or you could bring it back and buy something more appropriate

The cost of shipping to have this delivered makes sending it back not feasible.

[cottagefog]

If that's the polypond you purchased and plan on using... then use it!

My opinion if the 4" fits dead center within the ribs, then that's where I would install it.

Your TPR's will be a plus also.

With the tank being 12ft in diameter I bet there is enough flexibility where you could have the bottom slope towards the center ever so slightly during installation.

Koi (fancy carp) love the bottom of our ponds. Any debris that will build up on the sides of those ribs will be constantly swam over, disturbed looking for food. It will find its way to the center drain eventually.

Good luck and post pics!

[two_wheeled]

I think it will work just fine.