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Frequently Asked Pond & Water Gardening Questions (FAQ's)

Sealing a rock and mortar waterfall into a Koi pond. Do you have the knowledge or know someone who knows how to seal a rock and mortar waterfall into a Koi pond? The water seeps through the rock and mortar even after we have tried three different sealers and even placed a plastic sheeting behind the rocks and then reset the rocks. The water will even travel sideways and lead into my wall and crawl space. NEED

HELP!!!!! Thank You, Jim Patrick, Cedaredge, Colorado USA

ANSWER:I don't know whether you have 'Murphy's Law' or 'Sod's Law' over there, but it is essentially about the law of nature that if you think you have every possibility covered to stop anything from going wrong, but you leave the

slightest loophole in your plans or arrangements then it will go because of

that. In fact when you are building ponds you find that even other laws of

nature, like gravity, just go completely out of the window.

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What is happening there is a sort of capillary reaction. This can be quite

an effective way of siphoning a pool almost dry overnight. You get between

the inside walls of stone faced pools between the liner and the mortar of the

wall.

If you have soil or turf coming down into the pool, little capillary siphons

set up in the soil.

If water gets down behind the stone facing a waterfall, the pressure of the

water coming down the stream can push the water yards side ways because it

has nowhere else to go. The water in the pool can act as an air lock, or

just a barrier itself that aint going nowhere.

I had a raised pool that I built for someone that had a stone face down to

the marginal shelf about a foot down. It had a really long stream down to it

that would cause a fair amount of water to evaporate. It would lose about an

inch a day in the hot days of summer. BUT some days it would lose nearly a

foot.

The customer thought there was a leak in the stream, which we dutifully

dismantled suspecting mice having gnawed through the liner. No holes. That

took two of my three days.

What seemed obvious now was that the liner had something wrong with it

behind the wall because it never lost water below the level of the wall. But

before we dismantled the wall I asked the customer if perhaps he had filled

the pool right up to the top the night before there was a big leak. He said

of course he did, because how would he know that it had leaked some much

otherwise.

So then I asked how full he filled it. He said he just left the hose in it

and let it fill to over flowing.

Instead if dismantling the wall, drilled little holes in the pointing of the

capping slabs round the pond. And they solved the problem.

There was a little siphon setting up in the mortar that sucked the pool dry,

dragging the water up behind the wall and behind the outside wall, out onto

the gravel around it.

When we build waterfalls we insert little plastic tubes (about every foot or

18inches) between the stones at the base and these relieve the pressure from

the waterfall and provides somewhere for the water to drain. Also I use a

lot of smooth pea shingle to backfill behind big stones. That helps.

When I first read you email I though of the best sealant, before I thought

of the real solution. With every sealant there is a time when it eventually

packs in on you and you are back to square one. This is generally after the

first icy weather. Anyway, here it is. We have a product in the UK called G4

which I think is a cellulose sealant. What is good about is that you can

paint it cement or concrete when its wet and it will follow the water down

into the material to seal it deep down in. It also seals one material with

another. So if you had a wooden chute coming down to a stone sill, it would

seal the two into a unit. it is very useful for sealing in the lime that

washes off fresh concrete products into pools. Also, you can get in a black,

brown, green and red and clear gloss or matt. Brilliant stuff and stuff that

good doesn't come cheap.

IF you want I can find out where you get a G4 equivalent in the States, But

I'd recommend some experiment with a small masonry drill first. BUT mind you

don't drill through the liner!.

All the best

Pete