So it's Monday morning and I'm not firing on all cylinders yet... The new interpretation on "unblockable drains" only applies to layers of protection for single main drain pools correct?  This does not change any of the requirements for an ANSI/ASME approved stamped cover or sump dimensions right?  For me this is pressing as we are doing sump modifications and drain replacements in the next month, and I don't want to do all this work only go find out that I didn't have to...


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I only worry about it on single drains. The only change, I believe is they removed the 29" diagonal measurement. That dimension can no longer be used to qualify a system as unblockable. An unblockable system must be larger than 18 x 23 and then leave sufficient open area to prevent entrapment. I think with most drain covers this would be approximately 50% of the overall size. If I'm correct, which is a question, the cover must be at least 18 x 23 or 414 sq. in. + 50% or 207 sq in = total of 621 sq in. An Aquastar 24 x 24 unblockable is 576 sq in - 414 sq in = 162 sq in which is about 40%. This simplification is does not take into account the flow rate or design of the drain covers. I often use daisy-chain or multiple recessed covers, no demo and install all underwater. Call me if you have questions. I might be able to help
we do not have any single main drain pools, and all of my grates are a minimum of 22" x 22" or 484 sq. in. Right now the contractor is investigating the need to increase to a minimum 24" x 24" or getting custom stainless drain covers that will fit our 22" x 22" sumps. So if I interpret this correctly I am ok either way correct?
My understanding is that on March 1, 2010, the CPSC voted to accept language that allows for a drain fitted with an unblockable drain cover to become an unblockable drain. Therefore, a single main drain that is covered with an unblockable cover becomes unblockable and is not required to have the secondary systems. Since you say that you do not have single main drain pools, you only need to find compliant covers that will work with your sump and achieve the proper flow rate.


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