There's nearly 90,000 cesspools across Hawaii, and many could be polluting our groundwater.

   That fact prompted the state to offer tax-credits to home-owners to clean up and clear out their sewage, but very few have switched to safer septic systems.   

     A pair of former plantation homes on Oahu's North Shore were built in 1946. Inside they are filled with history. While outside they were equipped with cesspools, just like many other North Shore homes.

     "There is nothing but cesspools out here. The North Shore won't get a sewer system here. We are stuck with septic and cesspools but the majority is cesspools," said North Shore resident Shar Lyn Foo.

     But last year Foo took advantage of state tax credits to switch from cesspools to septic systems.

     "We converted to septic. We have a septic system on each side. Each cesspool can be converted to a septic system, but it takes a little more room for a septic," said Foo.

     That is because cesspools are basically just holes in the ground lined with blocks or concrete. While septic systems use a big tank and filter out waste.

     "What happens is the solids come out of the house and go into a tank, and the solids stay in the tanks. On one side of the tank there is a wall, and the liquid goes into a leech field or seeping pit," said Roger Seibel, Vince President of First Quality Environmental.

     All that filtering helps to keep waste from ending up in our groundwater, oceans or streams but it comes at a higher cost. 

     "It is a lot more in cost, about $25,000 to put in a septic system," said Foo.

     To help offset the cost, the state offers a $10,000 tax credit to eligible homeowners to make the switch.

     There are cesspools in nearly every Oahu community, more than 11,000 in total for the island alone. 2,100 of those are eligible for the tax credit.

     The state set aside $5 million annually to help 500 homeowners each year pay for the conversion but Foo is one of the few who have made the switch.

     "For 2016, we had 5 people and in 2017 we've issued at least 12," said Dept. Of Health Waste water Engineering Manager Sina Pruder.

     The state wants people to move away from cesspools because of health problems they can create.

     "A lot of them actually discharge their sewage directly to groundwater, which transports it to recreational waters and drinking water sources," said Pruder.

     Signs have been permanently placed along some Windward Oahu waters because of high levels of waste. Waste believed to be from cesspools. 
But this isn't just a problem for rural areas.

     "There are also areas in Honolulu, Black Point, Makiki Heights, Tantalus, and Palolo. Other areas that have cesspools," said Pruder.

     So what would encourage more homeowners to get rid of their aging cesspool?

     "The major deterrent from taking this credit is the price. Because you're spending more money than you are saving, that's the problem," said Foo.

     "People won't take advantage of the tax credit unless cesspool upgrades are mandated," added Pruder.

     Right now, the program is voluntary, but that could change under a bill advancing at the State Capitol. The measure would force homeowners with cesspools to finally make the switch to septic systems by 2050, but would provide grants to help some pay for the change.