Pond sealing problems

[mikeford]

Hi,

I'm hoping for some advice on a backyard pond that we recently built (pictures attached).

We've put down a concrete slab, built the walls from aac blocks, rendered, sealed and painted the exterior and used bitumen rubber to seal the interior.

After 21 days for the bitumen rubber to cure, we filled the pond and noticed a small leak at the rear. We emptied it and put another two coats of bitumen on, waited another 21 days to cure and filled again.

After 5 days of the pond running smoothly, it spontaneously sprang numerous sprinkler like holes along the bottom. We have no idea where these leaks are internally.

After rescuing our fish I'm now left with another empty pond and would really like to have it up and running before Christmas.

Ideally, I would like to avoid pond liners so as not to have a copping along the top. I'm looking for a suggestion to improve the waterproofing.

Thank you in advance.

 

[brokensword]

imo, with the type conc blocks (those are actually called slabs) you used, there's NO reinforcing anywhere, so not surprised you're getting leaks. The way to do this with conc blocks is to use 8" cinder blocks, stagger the joints, put in re-rod every other hole (best to also embed these rods into your footing, which should be below the frost line), then fill all the holes with concrete. This gives you the unified force holding container you need. Inside, plaster with cement (not concrete nor mortar) or hydraulic cement.

Now, that would mean totally redoing and I'm sure you're not thinking this direction, but at least anyone reading in the future (or you yourself might reconsider since it's empty) can see a better way to get a concrete pond built as these tend to leak simply because of being exposed to the changing seasons. A liner, imo, is definitely your best option but I'd still be worried that in time, the water pressure might push against your walls. It might crack them but hopefully, still hold water because of the liner inside. I know you don't want coping but you could easily put in a liner (epdm or hdrpe; NOT pvc or vinyl) and then either some sort of stone/concrete slab on top for decoration/finish, or even pour a custom top with concrete that sandwiches the liner between that will match your urban/utilitarian/modern look.

 

[combatwombat]

Welcome! I wish I could help, but I have no experience in block construction or rubberized coatings. I think a few folks on here have ponds like this, though, so hopefully they'll see this and chime in.

If it comes down to it and you have to go with a liner, you can order a drop in liner that will fit your structure perfectly and you can affix the edge of the liner to the structure with termination bars, so no need for a coping.

 

[Mmathis]

Hello and welcome! I have seen drop-in liners, as well. Maybe you would have less trouble with something like that, rather than always worrying if your masonry job is going to leak.

 

[GBBUDD]

Unfortunately i have to agree with the the block not being the best choice. While those blocks will withstand thousands of pounds vertically. There lateral support is not the best they are thin and have little resistance. All is not lost but it could cost a few bucks to complete . The staggering of your joints are minimal and should have been half way over the lower block You created what would be referred to as stairs and when block do fail even with a half lap stagger. They often will crack right through the center of the block and looks exactly like what you have with the stairs.

This is what you could do to make it work If you could get some sheets of aluminum or stainless like 1/16" or more and have that so it runs the whole length on both the front and back wall and top to bottom this will disperse your pressure points on the seams and take some of the strongest pressures from the bottom upward and around. Now the end walls you have staggered and I think you'd be ok without the sheet stock on the ends but it wouldn't hurt. Then and the part you don't want and that is the liner i would run it right up on the top secure the rubber with termination bars and then cap your contemporary water feature with some copper or stainless steel or even black anodized aluminum

There is also flat fiberglass sheets sold at the box stores 1/8" you could use that and put two layers on both walls this will make it pretty tough stuff once water is putting pressure against it. Depot also has Azek but it is not that strong but once it's backed up against the block it should do to disperse the pressures again stagger the joints as much as you can if it's a 8 foot sheet over lap them 4'

I see kids stuff in the back ground the best solution would be as @brokensword mentioned to use a hollow block wide and infill with rebar and concrete this will take a energetic youngin running to the water and pushing against the wall

 

[j.w]

@mikeford

 

[Mmathis]

BTW, what is the volume of the pond?

 

[mikeford]

Thanks for everyone's help. Seems like I should have come here before starting the build lol

 

[brokensword]

Thanks for everyone's help. Seems like I should have come here before starting the build lol

stick with us for the rebuild or just plain eyes-closed plunge forward; we'll take care of ya! Might involve a lot of liquid libations and if @addy1 raises the budget for 2022, you get cuts to the front of the line!!!

 

[GBBUDD]

Ok now the twirling eye masked musketeer was cute . one wearing a covid mask i don't see the benefit . If anything its helping people EXCEPT them and get in line . Not cool

 

[brokensword]

Ok now the twirling eye masked musketeer was cute . one wearing a covid mask i don't see the benefit . If anything its helping people EXCEPT them and get in line . Not cool

awwww, dona like ma twirling ninja pointy? Dis was ta sneak win da harley's pawrkd and da Hogmasta fas asleep in da hammocki!

Erm, Coovad? Wassat?

[insert silent and deadly emoji or...]

unleash the ninja again!!!!

 

[poconojoe]

There have been many threads on leaky concrete or block ponds. It seems to be a very common problem.

I wish you would have come here first. A moot point now...

Drop a liner in and be done with it.

I'm sure that sealer was expensive, especially with three or four coats.

All the money and time spent already could have been saved by using a liner.

There are many ways you can cap the top to hide a liner.

 

[Giovanni]

Hi,

I'm hoping for some advice on a backyard pond that we recently built (pictures attached).

We've put down a concrete slab, built the walls from aac blocks, rendered, sealed and painted the exterior and used bitumen rubber to seal the interior.

After 21 days for the bitumen rubber to cure, we filled the pond and noticed a small leak at the rear. We emptied it and put another two coats of bitumen on, waited another 21 days to cure and filled again.

After 5 days of the pond running smoothly, it spontaneously sprang numerous sprinkler like holes along the bottom. We have no idea where these leaks are internally.

After rescuing our fish I'm now left with another empty pond and would really like to have it up and running before Christmas.

Ideally, I would like to avoid pond liners so as not to have a copping along the top. I'm looking for a suggestion to improve the waterproofing.

Thank you in advance.

Hello, Welcome.
I built a concrete pond last year myself. And went through a lot of time and error in my thinking. but after fighting leaks I figured out my problem. The weight of the water pressing down and on the sides of the pond. This weight will open small cracks in the bottom and sides of your pond that are not apparent when it is empty. To solve this problem, the bottom of your pond will have to be much THICKER, also the bottom sides need to be THICKER the deeper you go to prevent the weight of the water opening micro-cracks. If you use concrete blocks, then fill those blocks with cement. My pond is 4 1/2 ft deep, 16 ft long, 8 ft wide; so the floor of the pond is 10 in. thick, and the sides are 7 in.