Project has 3 concrete water storage tanks in the cellar of the building.
Question 1: Does someone have experience for the preferred method of waterproofing the interior concrete surfaces of the tanks (6 surfaces)? Up for consideration is crystalline concrete waterproofing from Kryton, Xypex, Hycrete, etc. Anyone have good or bad experience with this method? Is there a manufacturer of surface applied waterproofing products for potable water storage tanks.
Question 2: Each tank will have a top hatch and a vertical access ladder which will be submerged partially or entirely in the potable water. What is the best choice for the ladder material? Stainless steel, aluminum, hot-dip galvanized?
Wayne, I had a similar application for a GSA project a few years ago under MF95. The tank was used for harvesting rainwatter, and was located in a basement. The tank was concrete and work included patching of cracks.
The preferred product was International Metalizing Corporation (www.intmetl.com) IMC 20-201 100 percent solids, two-component Epoxy Tank Coating.
I use Xypex a lot in architectural walls, decks, and footings, but not as a primary system. I would absolutely encourage you to spec it into the concrete mix, but for potable water tanks, you will want a primary inner liner. I have seen tanks with epoxy coatings, and also have seen sray rubberized applications such as Liquid Boot (are they still in buisiness?). However, all of these features are outside my area of expertise. I’m just posting to suggest some ideas to help.
Weve specified a few of those and have on the boards a large project with several large water tanks similar to yours, except that theyre on suspended slabs.
L.A. requires fire water tanks for large projects and weve tried cementitious with poor results; the crystalline coatings will not bridge cracks. We also tried fluid-applied urethane membranes (pure urethanes, not the modified types) and it worked well until the full body suit (that applicators have to wear when working in a tank) failed in one application and the applicator had to be pulled out of the tank fast so he could live another day.
Since that incident, we specify drop-in liners. They are attached at the top, above the water line, and are independent of the substrate so even if the latter moves, the liner remains watertight.
Straight PVC works well if the water is not contaminated. For the large project mentioned above, were storing grey water which may contain fats and oils (a no-no for straight PVC) so we specified an ethylene interpolymer alloy (EIA) with a minimum a minimum thickness of 40-mils.
The ladder should be stainless steel Type 302/304 works well, and should rest on several layers of PVC (do not anchor thru the membrane if you can) and be attached at the top above the liner and half way down thru the liner (thats the tricky part and careful detailing is needed).
I would probably go with either a fiberglass or type 316 SS ladder – I’ve had too many weird corrosion issues with 302/304 SS that is continually submerged. Agree with the comments about crystalline waterproofing – they won’t bridge cracks and in a seismic zone, you’re going to get them; and if there are other options, those options will always be better. I would call Tnemec too – they started out waterproofing concrete (“cement” ) water tanks and they know that market better than anyone else. Call Torin.
I would steer clear of crystalline and Tnemec and Carboline for this application and instead go with a CIM system (I used CIM 2000 for a very similar condition - it is the BOMB).
Looks like CIM 2000 has been updated/replaced with a new number, so you’ll have to get in touch with them to find out what they recommend.
Agreed a crystalline system won’t cut it. I’d go with a fluid-applied polyurea liner at roughly 100 mils. I’ve seen concrete tanks of many types lined with everything from epoxy to drop-in or heat-welded liners and polyurea seems to provide the best combination of strength, elongation, no seams and life cycle cost.
Yes, as with urethanes supplied-air hoods must be worn by the applicators but that’s completely normal for qualified applicators (I’ve never seen “full body suits” required, which would be interpreted as equivalent to a hard-hat diver suit - a fully enclosed, externally-supplied “environment”). Literally ALL fluid-system tank lining work has to be done using supplied-air systems; this includes everything from basement chillers to steel water tanks. All coatings I can think of displace oxygen and use of supplied air is a day-to-day part of the industrial coating trade. If a drop-in or heat-welded liner also used any type of solvent adhesive I’d require the same air-supply and retraction equipment as I would for a fluid-applied system.
Failure of air hood systems is extremely rare, but can happen - but retraction systems must legally be in place and manned/monitored so if a failure occurs the system users are out of the danger zone in seconds with no action on their part.
It’s considered less of a danger than swingstage work, where out-of-date or worn out harnesses, illegal rigging and such often go unnoticed.
As usual Jim’s advice and experience is appreciated.
The PVC liners, unless they exceed a certain size, can be prefabricated in one piece and pre-tested. If not, they’re heat-welded once in the tank with seldom more than one seam; I don’t know if the heat welding consumes much oxygen, but if it does the quantity must be small.
I actually like the seamless polyuera, but when burnt once I seldom re-visit the same material.
I just noticed that Wayne mentions 6 surfaces. The sixth is the underside of the tank cover which is not in contact with water but gets a lot of condensation.
When using a liner, we specify crystalline WP for the cover. I imagine that if poyurea or other liquid-applied WP is used, it’s going to be difficult to spray overhead and the applicator would have to roll the material in multiple coats to achieve the required mill thickness. The same difficulty applies to same extent to troweled-on WP.
I’ve used Tnemec Series 264 on similar projects with no problem. With regards to applicator safety (granted that this is means and methods and accidents do happen), that presents another reason to use a product line that requires that knowledgeable applicators be involved.
CIM coatings were very good in immersion conditions in the past but I can’t find CIM 2000 on their website any more. I’ve never used any of their other products.
Whatever product you use, make sure it’s designed for immersion service. Temperature can come into play as well; freezing conditions even moreso.