Replacing a Main Drain Sump

[CPO]

The pool where I work was built in 1970 with concrete and a ceramic tile surface. It holds 100,000 gal and has a single main drain which is gravity fed to a D.E. filtration tank that has a max output of 225 GPM. The main drain is about 27"Lx22"Wx24"D When the pool was drained to replace the lighting, the old metal sump was so rotten that it literally vacuumed out by shop vac. A 6" pipe leads under the pool to the filtration room at the end of the pool.

I assume we'll fabricate a new sump inside the dimensions of the old (but the same depth) out of poured concrete. We could drop in a fiberglass/plastic ready built unit, but either way, I have the same question.

If we are to install a new sump, how do we create a watertight joint both to the old concrete as well as to the old pipe?

 

[JamesW]

You should probably get professional help on this to make sure that everything complies with code, including the Virginia Graeme Baker Pool and Spa Safety Act. You might need to put in two drains in place of the single one.

You might be able to eliminate the main drain, or convert it into a return, if you have sufficient suction from skimmers, but that's unlikely.

 

[CPO]

Because the drain is gravity fed and not connected to a pump, we do not need to go to extremes (2 drains, etc). The cover is the only mandated change. As long as the sump shape meets regs, it is good to go.

The 'Professional Pool Company' said, and I quote, "Any concrete guy will know how to make it water tight." I've brought a few in to look. Unfortunately, they don't.

So...how is this done?

 

[JamesW]

I still recommend that you get a qualified professional to certify the design before construction and the installation afterward. If this is a commercial/public facility, then you will also need to get the installation certified by the inspector before putting the drain into operation.

I think that this should be done by a qualified professional.

 

[CPO]

There is only one 'Pool Professional' in our region who handles commercial pools & they are too busy shutting in residential pools to be bothered with a 'simple job' like ours. They told us to work with a concrete guy who would know what to do. They didn't, nor have any other concrete person who we've brought in.

So the question remains, how would you make a water tight joint between the old concrete & new?

 

[CPO]

Painting a Main Drain Sump

So...good news. For the first time, one of the contractors actually poked around a bit & they found that what everyone had though was the disintegrated remains of the sump was actually just rusted scale built up over the last 40 years. From what we can tell, the box is likely intact & potentially serviceable.

This is good because they used a welded steel pipe to run to the filtration room & this pipe may not survive the removal of the sump.

The recommendation is to clean out the muck & remove the rust with a knotted wire wheel & then paint the box with an industrial 2-part epoxy similar to that used to seal underground tanks.

Any thoughts, brands, etc?