How do the standpipes connect? Surely just a press fit would leak with the pressure of a 30 inch high water column. if you just PVC glue them in, they can't be removed. If you put a male threaded adapter on the end of the standpipe, and a female threaded fitting in the hole in the tank, does it leak? Does it have to be done at the factory before they seal the overflow towers in place inside the tank? If I ever had to change the bulkhead fitting on the drain holes, it starts leaking, I'd have to drain the tank, and then remove the overflow tower box thing, then change the fitting, then replace the overflow box?