Tank Construction - major problem

[nhjohn]

I'm well into the process of constructing my 1800 gallon storage tank in a crawl space. Three walls are concrete, one wall is a combination of dirt and wood. The floor is also dirt. A problem I knew I was going to have was the fact that a little water gets into the crawl space when it rains. In order to keep the standing rain water (about an inch at most) from the tank insulation I bought a second EPDM liner. So I would have the insulation sandwiched between the EPDM liner. I even raised the tank up a little with bricks and treated lumber so that the water could flow under the tank as I knew it would over time anyway. Last weekend I put the first liner in. Today, when I went down put the insulation and second liner in I noticed something: Condensation! - on the inside of the first liner. Basically if I go forward, the condensation will eat away all the insulation. This must be from the water on the other side of the liner.
Unfortunately, I don't think there is anyway to stop the in flow of water as it comes up from the ground.

Any thoughts as to what to do? Thanks very much

 

[Nofossil]

Condensation can't pass through EPDM, so the condensation is from the air on the side where the condensation forms. Condensation happens when there's a surface that's cooler than the dew point of the surrounding air. I assume that the space between the liners will be sealed, so you shouldn't get ongoing condensation. Right now, the outer lining is probably against cool dirt, and the moist summer air condenses on it.

 

[free75degrees]

You might want to consider an insulation that can get wet like the stuff they use for ICFs. Is it polystyrene? If so, polystyrene is not great at the high temps, but you could probably use it on the bottom layer(s) with a polyisocyanurate layer to isolate it from the hottest temps.

 

[Reggie Dunlap]

The condensation is formed when warm humid air meets the cool dirt. The best solution would be to install a layer of 2" foam over 6" of stone, then pour a 2-3" slab over the top. The foam keeps the slab at room temp while the slab helps seal out groundwater.

What causes the water to get into the building? Gutters might help. Does the grade slope away from the building? Are the footing drains clogged?

 

[jebatty]

Seems to me that once the tank is in operation and the water is hot, your condensation problem will cease.