Putting butyl rubber liner in old concrete pond (should i make sure water can drain through concrete base)

[Davidp]

Hi all!

I have uncovered an old concrete pond in the garden (approx 16ft x 5ft x 3ft deep). It has some cracks from about half way up so doesn't hold water, but does holds water very well in the bottom 18 inches or so. I'm planning to restore it to use by adding a butyl rubber liner (partly as I've raised the level a little using some wooden sleepers).

My question is whether i should drill through the bottom of the concrete to allow any water that gets between the liner and the concrete to drain away from under the liner? I guess it shouldn't be necessary but is it a good precaution?

Thanks for your advice!

David

 

[Jhn]

Yes, put holes in the concrete so water can drain otherwise you could end up with a hippo in the pond.....ie water gets under the liner and pushes it up.

 

[j.w]

@Davidp

 

[GBBUDD]

I would also do one of two things
1. round all the edges of the concrete as and sharp or even pointed can cut the liner over time
2 . use a quality non woven underlayment


I also agree with @Jhn that yes i would drill a few decent sized holes at least a 1" fill the hole with some gravel that won't stop drainage

 

[brokensword]

Yes, put holes in the concrete so water can drain otherwise you could end up with a hippo in the pond.....ie water gets under the liner and pushes it up.

@Jhn ; I have a question--if this concrete pond is already leaking, i.e. has a path for any water to escape outside the concrete shell, would drilling holes still be that necessary? I can see that it wouldn't hurt but I'm wondering how much work (how thick the concrete is) this would be.

Just wondering especially since the cracks are almost at the bottom anyway. Water that got under would be forced up and toward the cracks before building enough to lift a liner, wouldn't it?

 

[poconojoe]

If you have the tools readily available (or borrow) to drill the holes, ie: rotary hammer (aka hammer drill), then why not do it?

GBBUDD's ideas are spot-on. Smooth the sharp edges. Definitely fill the holes with gravel to prevent clogging and also prevent your liner from stretching into the holes.

It would be disappointing if you didn't provide drainage and had problems later. The liner is the very base of your pond with everything built on top of it. Plus your fish and plants would need to come out. Not fun and bad for you fish.

You mention buytl rubber as a liner. I hope you mean 45 mil EPDM. That is the preferred material. And yes, non-woven underlayment under the liner. You can both together.
Do not, no matter how cheap it is, use a PVC liner. Ask me me how I know....

 

[JamieB]

Don’t ask, the soap box gets stepped on! ( it gets brittle fast, and tears easy)

 

[addy1]

Welcome to the forum!

Carpet pad works great as a underlayment. imho 10 years later it is still intact. I bought new cheap carpet pad.

I would make sure none of the concrete areas hold water.

 

[Tugaloo]

That will make a great place to support a liner pond. With any pond, water collecting under the liner is not good.
You are just using the concrete for support, so busting up the bottom or making large holes is a plus. It may be wasted effort, but could avert a problem that may surface over time. You can get old carpet from stores they have ripped up. Use that so sharp edges will not cut the liner.

 

[Jhn]

@Jhn ; I have a question--if this concrete pond is already leaking, i.e. has a path for any water to escape outside the concrete shell, would drilling holes still be that necessary? I can see that it wouldn't hurt but I'm wondering how much work (how thick the concrete is) this would be.

Just wondering especially since the cracks are almost at the bottom anyway. Water that got under would be forced up and toward the cracks before building enough to lift a liner, wouldn't it?

Yeah, I don’t know if it’s necessary really, but if it holds 18” of water in the bottom I wouldn’t chance it. Could drill holes or just get an electric jackhammer To provide drainage. I have a background in construction, so drilling holes in concrete isn’t that big a deal to me.