Sealing my underground reservoir

[CL "dnoyeB" Gilbert]

I am laying the blocks for my underground reservoir. This will hold water to be pumped onto my lawn during summer months.

My question is, I plan to seal the inside of the reservoir so it can hold water. Is there any need to seal the outside with tar or anything? Water infiltration is not a problem because its meant to be wet. I want to make sure though that water infiltration will not damage the integrity of the thing. I think the normal way is some kind of tar painted on the outside of the blocks?

Also, do I need drain tiles around the perimeter? Again, I don't care about wetness because its meant to be wet on the inside. If I do drain tiles, then Ill need to do some kind of drain as well. Not looking forward to that, but more not looking forward to the thing breaking either.

CLG

[Don Phillipson]

We may need to know first if it is the size of a barrel or the size of a swimming pool.

[Steve Barker DLT]

Yes, depending on the size of this, you'll need perimeter drain and a sump. Otherwise it runs the risk of floating out of the ground during wet seasons. Or, collapsing from the pressure.

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[RickH]

At some point you will wish you had installed a bottom drain, even if it cant be a gravity drain its not just a simple nicety to be able to hook a pump or open a valve to a bottom drain, its a necessity at some point. Are the blocks hollow or solid? If hollow then an outside membrane is less useful because and water infiltration will creep down the block interiors.

[CL "dnoyeB" Gilbert]

The pit is about 5' by 8' and 5'6" deep. There is no wet season here. The ground is always the same wetness year around. At least by my house. Do they install this type of thing on septic tanks?

The water level is about another 6" down. At least that is where the dampness started and I stopped digging.

CLG

[trader4]

=A0The

Inquiring minds want to know, why didn't you just install an irrigation well? A hell of a lot less work and the water is available in essentially unlimited amount, without regard to when it rained last.

[dadiOH]

Your tank will hold roughly 1,750 gallons when brim full. That's enough water to put 1/2" of water on a lawn of 5,280 square feet. One time. I hope you have a small lawn or rainy summers.

If you are worried about the integrity of the thing I hope you are using steel. Lots of steel. And for the top course of block I'd suggest "lintel" block - blocks with a horizontal, semi-circular depression in which one lays steel and then grout (runny concrete); they tie the walls together. And fill all the block cells that have vertical steel with grout too (first, knock a hole in the bottom cell so air can get out). You going to have a lid for this thing? How/what?

All in all - had I wanted such a tank - I think I would just have bought a pre-cast septic tank. Where I live, one that size or close to would run maybe $1500 installed.

[BobK207]

per dadiOH's analysis (& I agree with it)

your tank really doesn't make much sense ...to build or even buy

lawns are thirsty things your tanks needs 4 to 8 times the capacity to make any sense

cheers Bob

[Bob F]

Inquiring minds want to know, why didn't you just install an irrigation well? A hell of a lot less work and the water is available in essentially unlimited amount, without regard to when it rained last.

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Look up "sand point", and, if you can find it, Brady PVC well points. Brady seems to have been bought by another company. I can't find the points on the new page.

[terry]

Like somebody said. Humans are foolish. They expect water fountains in the middle of a desert; like in Las Vegas! Water will eventually cost several dollars per gallon (like gasoline). For lawns plant clover not grass. Needs less cutting, less water, less liable to pests and returns nitrogen to the soil thereby building it up, instead of, like grass, needing constant watering and fertilizing! But easy to preach when one lives where the climate is cool, lots of ground water and it rains frequently!

[CL "dnoyeB" Gilbert]

I am not asking for an evaluation of the functionality of the cistern. This has been vetted on this group already.

I am asking about sealing it or not.

[CL "dnoyeB" Gilbert]

Because this is not for rain water. Its for the gallons I pump out from under my house every 10 minutes.

Also because I enjoyed making it. I have not worked with cement or blocks before. Its good experience before I start on my back porch / patio.