School pond losing water

[Gfishschool22]

Good day all! I'm new to this forum.  First off thank you Aquarium Co Op I love all your videos and information. I'm kind of new to fish keeping(a little over a year now) I will try to make this as shirt as I can. I have 5 indoor aquariums and a quite large outdoor pond with goldfish(comets and shubunkins) They did great over winter, so well they had babies in spring. So what to do with the babies since the stores nearby won't take them or they will "take care of them for me" ...I'm a roomparent and regular sub at my childrens school and we have lovely patios for planting etc. We moved rooms and got a new patio ove the summer perfect for an outdoor fish pond the children absolutely love. I have a HUGE problem though and I'm quite stumped as well as the teachers at the school. So I dug the pond, used my pond liner I got from lowes, made my diy filter with pump and tubing from lowes used a new flower pot have lava rock and inside of pillows throughout for filtration media and sealed the outspout with outdoor strong silicone.  Have a small papyrus in and a couple hide pots. I first made the mistake using the schools water which is different from my at home well water. Unfortunately we had some floaters. So then I said let's wait a longer period for the chlorine and heavy metals to stabilize before more fish. We added mire fish everything was great then all of a sudden over night it was down to about 2-3 inches of water when we came in the next day. Instead of filling it up with school water, I took the fish out took them home and took it all apart to see if a rodent had chewed a hole in the liner and check all my plumbing (that's still new) wasn't leaking etc. Stumped nothing have no idea. So brought from home extra tarp to put underneath put the liner back in set it up filled it completely let it set running like normal only without fish for week and half, all is good so we added fish...Literally within a couple days it's happening again!!!!! What in the world could be happening? There is no leak anywhere and we're in the south but it's not sweltering weather to make it evaporate this quickly.  Kids teachers and I are all starting to get bummed. Help please if you can !!! I added an old pic from the start when it was great and the other day

[Chick-In-Of-TheSea]

Is your liner all tarps or do you have a rigid one as well, like this?

https://www.lowes.com/pd/MacCourt-71-in-L-x-58-in-W-Black-High-Density-Polyethylene-Pond-Liner-125-Gallon/3389466

[gardenman]

I was going to say it could be critters drinking the water, but the netting pretty much precludes that. A small herd of deer can drink a lot of water overnight. I would say you have a leak someplace.  Someone who doesn't like the pond may be intentionally sabotaging it by poking a hole in the liner when no one's around. It happens. We had a local fish store have someone drop mercury into their system which almost put them out of business. A few layers of cheap poly (the 10'X25' rolls are pretty cheap) under the existing liner might solve the problem for much less money than a new pond liner.  The poly doesn't last long in full sun, but under another liner it can last a long, long time.

[Tanked]

 

Think like a raindrop.

There really are only 2 possibilities: Leakage or evaporation.  Evaporation isn't that fast, even on a windy day.  If your pond drops to the same level every time the water disappears, that is about where to start looking.  You should be looking for small slit or crack, and places where damp or wet soil should not be.  If you roll back the edges of the liner and find wet soil you have a leak.  The area around the pump/filter should be totally dry.  If you are filling your pond close to the edges, it is possible that the plants on the left side, even the power cord are wicking away some of the water.  Washing down the liner, and looking for a puncture is the cheapest option, as repair kits are available.

[modified lung]

Where does that black tube in the lower left corner lead?

[Gfishschool22]

On 10/31/2022 at 10:57 AM, Chick-In-Of-TheSea said:

Is your liner all tarps or do you have a rigid one as well, like this?

https://www.lowes.com/pd/MacCourt-71-in-L-x-58-in-W-Black-High-Density-Polyethylene-Pond-Liner-125-Gallon/3389466

I have a tarp underneath and this one is the one I got from lowes I have it on top of the other tarp

https://www.lowes.com/pd/smartpond-84-in-L-x-120-in-W-Black-PVC-Pond-Liner-200-Gallon/1000862966

On 10/31/2022 at 11:17 AM, gardenman said:

I was going to say it could be critters drinking the water, but the netting pretty much precludes that. A small herd of deer can drink a lot of water overnight. I would say you have a leak someplace.  Someone who doesn't like the pond may be intentionally sabotaging it by poking a hole in the liner when no one's around. It happens. We had a local fish store have someone drop mercury into their system which almost put them out of business. A few layers of cheap poly (the 10'X25' rolls are pretty cheap) under the existing liner might solve the problem for much less money than a new pond liner.  The poly doesn't last long in full sun, but under another liner it can last a long, long time.

Thank you. Wow mercury, that's awful! We thought about putting up a camera

On 10/31/2022 at 11:42 AM, Tanked said:

 

Think like a raindrop.

There really are only 2 possibilities: Leakage or evaporation.  Evaporation isn't that fast, even on a windy day.  If your pond drops to the same level every time the water disappears, that is about where to start looking.  You should be looking for small slit or crack, and places where damp or wet soil should not be.  If you roll back the edges of the liner and find wet soil you have a leak.  The area around the pump/filter should be totally dry.  If you are filling your pond close to the edges, it is possible that the plants on the left side, even the power cord are wicking away some of the water.  Washing down the liner, and looking for a puncture is the cheapest option, as repair kits are available.

Wow, I wondered about the plants bit didn't think about the power cord

On 10/31/2022 at 12:41 PM, modified lung said:

Where does that black tube in the lower left corner lead?

One front left is power cord one by pot is tubing from pump up into pot

[nabokovfan87]

On 10/31/2022 at 6:40 AM, Gfishschool22 said:

then all of a sudden over night it was down to about 2-3 inches of water when we came in the next day. Instead of filling it up with school water, I took the fish out took them home and took it all apart to see if a rodent had chewed a hole in the liner and check all my plumbing (that's still new) wasn't leaking etc. Stumped nothing have no idea. So brought from home extra tarp to put underneath put the liner back in set it up filled it completely let it set running like normal only without fish for week and half, all is good so we added fish...Literally within a couple days it's happening again!!!!! What in the world could be happening?

One thing to keep in mind is that the water weight would stretch the materials.  I would take a look at some of pondguru's very old videos when he was building ponds and just double check construction against how your liner is installed.  One thing to note is that you could be dealing with a small hole and as the pond fills, the liner is stretched and then that opens up the hole. 

Maybe this will work.... but fill the pond with a dye substance that is fish safe like methylene blue / Ich-X and then let that sit for 24 hours.  Take apart the pond carefully and inspect the underlay for anything that has been stained. This would give you an idea of where to inspect on the pond liner and/or ground to alleviate any issues. 

Secondary to that..... set the liner up on concrete in some capacity and do a leak test.  If it doesn't leak above ground, then you isolate the variable to being the ground itself and you can further inspect things like the ground being level, overflowing in a spot, etc.

I know there's a few hundred "how to build a pond" videos on youtube, this is just one source I know of that seems pretty decent for building a pond and has a lot of videos and tutorials.