Not being a smart ass but those words in the same sentence bring me nightmares;
Holding - tank - sealant - black.
There is a company in Southern California called Inca Plastics, perhaps it is better to put in a new black tank?
In the first few weeks of ownership before I lifted my rig 3 differebt times higher & higher, I got beached driving very slowly in a restaurant parking lot - the mickey mouse operation known as MEYERS RV (now out of business), tried sealing everything but its a truck, not a house, its always subjected to forces - I limped along for a year with that gray water smell surrounding my rig.
Changing it out, instant peace of mind.
2005 Roadtrek Versatile 190-a super modified & efficient Lifted Rig with a reconfigured Battery Box with 2 x 225ah Lifeline AGM 6 Volt Batteries, 250 watts Solar, Victron BMV712 Smart Meter, Victron MTTP 30/100 Smart Solar Controller, Magnum MMS1012 PSW Inverter Charger & OEM Onan Generator. Plus...