Insulations for ground domestic water tank 2

[fcu45]

Hi
In my current project there is pretty large ground domestic water tanks plan dimensions 60' by 35' and 5' deep.
It is made of reinforced concrete with water proof admixture.
My question is regarding the internal water insulations that should be placed.

For now There is only epoxy coating shown in the drawings.
But shouldn't be some water tight membrane fixed into inside surface?

Regards

 

[normm]

If the reinforcement has been correctly designed to limit the crack width, the water-tight membrane is not essential in my opinion.

 

[JedClampett]

Water proof admixture-Waste of money
Coating (even epoxy)-Waste of money
Leak resistant structures are dependent on waterstop details, limiting pour areas, limiting water to cement ratio, proper reinforcing and skilled labor. As much as admixture representatives and coating salespeople give you the hard sell, they're not necessary.

 

[rjenyoy12]

I agree with the above comments that waterproof admixture and/or coating are not necessary. Special liners or coatings may be used to protect the concrete from harmful liquids but in your case considering that these are for domestic water then no need for such application.

 

[fcu45]

Hi thanks dear colleagues

JedClampett where should I start ?
Contractor is having pretty poor workmanship and quality control isn't much of his interest. Mix was pretty stiff with 2 inch slump and tank walls are only 8 inch thick.

There is only one construction joint below water level (Just above base slab) and it has the required water-stop.

Anyway, from your responses the external wall surface water proofing required by drawings seems to be sufficient "Although there may be walls reinforcement corrosion in the long term".

I appreciate your inputs
Regards

 

[JedClampett]

Eight inch walls are going to be problematic in any case. It will be hard to install waterstop in an 8 inch wall. Plus, even though the tank is shallow, I would expect cracking at the vertical corners.
If it's too late to redesign, I would go with either a epoxy coating (OK) or a HDPE liner battened at the corners and top (best). Another choice is to live with the leakage. The trouble with the epoxy is that it will tend to crack with the concrete and transmit leaks and eventually corrode the reinforcing.
Battened liners are pretty cheap (~$2.00 a square foot?) and effective.

 

[cvg]

perhaps something should be done to increase his interest in quality control. I might suggest withholding payment on work that is demonstrated to be not in compliance and require replacement where the structure does not meet the design.

 

[shobroco]

External waterproofing sounds like trouble. The water is inside the tank & the moisture will migrate out & make the coating, whatever it is, peel. Cisterns are poured in my neck of the woods every day & as Jed says, good concrete, good detailing, and good workmanship is all they need to work well & last indefinitely.

 

[fcu45]

Thanks dear colleagues
Dear Jed I have googled about Battened liners and they seems great solution, but my manager isn't much interested telling me he always used epoxy internal coating.

@ cvg you are correct
In fact I had big fight with their manager, and mentioned it in today's meeting regarding that issue.

@ shobroco that is much logic but they are following the drawings.

Thanks again everybody
Best regards

 

[JedClampett]

To be clear to everyone, all the liners and coatings i suggested are meant to go on the water side of the vessel.
Another idea that is probably too late to implement is a leak test. We always require it. Contractor fills the tank, measures the level, waits for 24 hours and measures the level. You deduct for evaporation and figure it out. We allow .1%