Sorry to hear your basement flooded. BUT, exploding appliances is nothing to full around with. Who told you this? You should check with qualified people, perhaps your gas company, and get the correct answer. I would not depend on a forum to give me an answer.

I have what could be a similar problem in my garage. I had to core into the ledge to get the foundation in which lead to water seeping and a difficult way of coring another hole to put a sump pump in. I do have a utility pump placed in a cut down drywall bucket (could only get so deep) and set it up on a timer. What I learned was I only needed it to run for less than a minute to get the garden hose running and it siphons the balance. Don't know if you have a lower point in your yard near by to do the same. Works for me, hopefully can work for you.

Actually, after futher review of what happened, it was maintenance that possibly (kinda sorta) contributed to the water leak. The day before the leak, I was doing maintenance on my washer and dryer. I was cleaning the lint from the dryer vent. Also, I was cleaning out the washer tub. I think I must have moved the utility sink a bit and caused the pex supply line that goes to the sink to move a bit, maybe causing it to loosen and then the heat and water pressure built up and popped the hot water supply line out of the bottom of the faucet connection. Either that or the rubber o-ring just gave out from the heat and water pressure. So, I changed both lines to the steel braided type that I have on my washing machine supply lines. This should hopefully prevent any further issues. And, yes, live wire oak, although you seem to assume I do not do maintenance around my house, I do indeed regularly perform maintenance around my house, to include: flushing the water heater twice a year, cleaning the dryer vent, cleaning the gutters, cleaning and servicing my water softener, changing the carbon and sediment filters for my well water, prepping and staining my deck, lawn/landscaping maintenace, maintenance of lawn equipment (riding mower, trimmer, blower), maintaining and cleaning of pellet stove, maintenance on two automobiles....etc...etc...etc... I guess I have to add inspecting supply lines to that list. And, yes, brickeye, I could not agree with you more. Maintenance is less work than paranoia......that is why I try to do as much as I can around my house to avoid the catastrophes..... thanks. mm

"I've never seen one just dump into soil under the slab. That would be silly. They typically are connected either to the perimeter draining system or to their own catchment (dry well)." Silly or not, terminating a floor drain directly into the soil under the slab was common practice for and decades decades and is a practice that continues to this day. Although modern plumbing Codes require floor drains to be trapped and discharge into the building's sanitary sewage system, modern plumbing codes are not yet adopted or enforced everywhere...and the practice of terminating the drain into the soil under the slab continues unabated in many locations. If the original poster's house was constructed prior to the 1970s, it is a safe bet that no connection to either the sanitary or storm sewer system exists. That said and that being the case, it would account for all the symptoms described by the original poster and an increase in the pumping capacity of groundwater under the slab would be the typically remedy.