12 years... please replace it. Undercouter leaks are very common and costly due to old RO systems. For liability reasons if I were working the field I would not even touch it.
That being said, RO systems don't regenerate. They are a self cleaining filter and should run to the drain then they are filling the tank. There are really only a few item that go wrong in an RO.
1: Auto Shutoff Valve (ASV). This is a simple pressure switch that shuts the inlet side of the RO membrane off when the tank reaches 60% of the incoming line pressure. This uses rubber diaphragms and a plastic piston that is prone to wear. If this item fails the system may not shut off and will continue to drain and it can also allow untreated water to croos over into the product water stream
2: Check valve, the Check valve is located after the membrane permeate. The check valve can be integrated into the membrane, or it can be inside a fitting on the RO system, or it can be an external piece located on the permeate tube. This valve prevents water from flowing back from the pressure tank through the membrane and down the drain thereby lowering the pressure In the tank and causing the system to cycle on/off. Back pressure on the membrane will usually damage the membrane.
3: Drain Flow Restrictor. This limits the amount of waste water going to the drain. A missing or "blown" flow restrictor can cause excessive waste water and often times does not allow the system to build up enough pressure to push water through the membrane thereby the tank does not fill and the drain water will continually run.
4: Pressure tank. These fail on a regular basis. Sometimes they last 10+ years, other times they last 1-2 years. These must be drained completely of all water and the air pressure should be set to 6-8 psi.
The advent of online sales of this equipment has really pushed companies to source lower and lower quality components in order to be the lowest price. I have consulted with companies on tens of millions of dollars in claims due to leaks from this type of equipment. I am surprised the Hoeowner insurance companies have not been more aggressive on writing this type of equipment into their disclaimers... but many of them are taking serious notice and I expect this to occur within a few years. Insurance companies move very slowly. I have worked with companies that manufacture these units in China, complete for under $50 and the quality... lets just say I wouldn't put these units in my enemies house, not would I let a dog drink the water coming out of them.
A good quality RO is going to cost more than $100 on Amaz.., and the components are not going to all be made in China with a "Made in USA" Sticker on the box.
A real made in the USA RO is going to be more expensive but is worth the extra few bucks. Be careful, almost every RO claims it is made in the USA, but almost none of them actually are. The vast majority of components are made by the lowest bidder, in the nastiest factory... ignore 90% of what you read on te companies websites, this is just garbage marketing...
