Expert: Roger Zona - 4/27/2011

Question
QUESTION: Hello Roger,
What is the normal pactise of waterproofing a swimming pool water storage tank?

I am working on a project where the tank has been built and not correctly sealed. There are some pipes coming through the tank near the bottom that have not been properly sealed.
Can you recommend any products that I could use to seal the tank without demolishing it. I have 67 such tanks on my project.

Thank You
Marc

ANSWER: Hello Marc,

I understand your question but I don't have enough information.  For example, what is the storage tank made of - steel, concrete, plastic, etc.; how large is the tank; what is the purpose of the tank; what are the penetrating pipes - metal or plastic?

As you can see, the problem cannot be properly resolved without full disclosure.  Send me a follow-up email with the information and I will attempt to give you the best advice I can.

Thanks for your inquiry.


Roger
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---------- FOLLOW-UP ----------

QUESTION: Thank you roger,
the tank is made of concrete (i think bad quality).
The penetrating pipes are PVC.
The tank is about 1000 U.S gallons capacity.
The purpose of the tank is to store water for a swimming pool.

Answer
Hi Marc,

That information helps.  There are two ways the pipes could be inserted into the tank: 1st, the holes for the pipe were drilled into the concrete and the pipes inserted after the tanks were cast; 2nd the pipes were in place when the tank was formed and the concrete was poured around the pipes.

The 1st method would leak since a water tight seal between pipe and concrete would be difficult.  The 2nd method is more likely but could leak because concrete shrinks upon curing and concrete is, by nature, porous and will absorb water.  

In either case, a suitable caulking material should do the job.  There are many varieties available so be sure and read the labels to find one that adheres to concrete and PVC.  Apply the caulking on both sides of the pipe - inside and outside of the tank.  Appearance should not be a concern.  Also, the caulking should be re-applied every 6 months or sooner if the leaks develop again.  You may also want to consider painting the inside and outside of the tanks with a waterproof coating.  Again, there are several products available.  A latex base paint that adjusts to expansion or contraction is good.  Also, other sealants are colorless and are absorbed into the concrete surface.  They need to be re-applied also.

I hope this has been helpful

Roger
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