Boats of a certain vintage are often equipped with original freshwater systems composed of so-called Qest fittings and tubing made of polybutylene. To say that this stuff is prone to failure (cracks and leaks, that is) is something of an understatement. And trying to repair a broken coupling or stretch of poly is often difficult and usually results in subsequent heartache—the stretch continues to leak, albeit just in a different spot.
The fix is simple, though, albeit a tad expensive. Replace that outdated poly system—or as much of it as you can access—with PEX tubing and SharkBite fittings. For our money, the PEX/SharkBite combo is the easiest to use, most state-of-the-art solution for the onboard plumber today.
The tubing is color-coded (red for hot and blue for cold) and the push-to-connect fittings do away with all the complexities associated with other methods. Indeed, the only extras you’ll need to buy, whether for a big job or a small one, are a special tube cutter ($10 to $15) to cut tubing to the appropriate length and a deburring tool/depth gauge ($10 or so) to smooth out after-cut roughness and mark precisely how far a length of tubing must be pushed into a fitting to properly seat.
Of course, if you can’t replace your whole poly system, remove as much as you can and then simply add PEX and SharkBites from the place or places where you terminated the old system. SharkBites are compatible with poly. In fact, most good hardware stores sell fittings that are specifically designed (and labeled) for poly-to-PEX conversion. And while SharkBites are pricey (a simple, ½-inch coupling costs between $7 and $8), PEX itself ($10 for a 10-foot section of ½-inch tubing) is dirt cheap.
Two things to watch out for. Don’t try to save money by skipping the purchase of a pipe cutter and going with some other device you happen to have on hand (like a pocket knife or a pair of sidecutters)—the ends of the tubing must be cut square and the best way to achieve this squareness is with a high-quality tool you’ve purchased for the purpose. And second, make sure you use the depth gauge on every cut—not doing so may eventually leave you wondering if you’ve pushed a length of tubing as far into a given fitting as it needs to go. Tubing that is not properly seated in its fitting will most likely leak.