Rainwater Plumbing: Tank to Destination

Now that the water is in your tank, how do you get it out so you can use it? 

We could hook the tank up to the regular water tanks pump, but what if something we don't like got into the rain water tank? How would we get rid of it without contaminating the rest of the tanks?

The simple idea of having a tank full of rain water quickly became a concern about damaging the rest of our water supply. The decision was made that the rain water tank needs to have a purge hose that we can drain its contents should we decide that it has become compromised. I thought about making a very complicated valving system where water from the rain tank could be tested and purged if desired without going into the main tanks or, by opening some valves, used in conjunction with the rest of the water tanks. This idea, while complicated, seemed like an adequate solution.

The only caveat with this plan has to do with the flexible water tank and its durability. Flexible water tanks are a great way to get water tankage into small nooks in the boat where a regular tank would be difficult to install or fit. The problem with flexible water tanks stems directly from this flexibility. 

As the yacht bounces around in the seas, the water inside the tank will slosh around. In a rigid tank, the contents move while the tank remains un-phased. In a flexible tank, the contents of the tank move along with the tank. This constant sloshing will wear on the seams of the tank and lead to the eventual death of the flexible water tank. It is best to use flexible water tanks only for a short period of time and then store them drained and empty while underway.

If we use the rain water tank as part of our water tanks, it will suffer greatly from constantly flexing as it is the lowest tank and would stay full the longest. The alternative is to fill the tank with rain water and drain the tank instantly into the other water tanks through a hose with its own pump.

This would satisfy all the needs we have placed upon the flexible water tank. It would allow us to test the water, purge if undesirable, and maintain the tank empty for as long as possible. We also don't have to worry about accidental contamination from the flexible tank to the other tanks because there would be no direct plumbing fitting that could be left open and cause a disaster.

The flexible tank drains via a small 1/2 inch water hose that is led to a high powered water pump. This pump will flow 4 gallons per minute at 60 psi through a hose that will allow us to test the water, and if we like it, dump it into the main tanks. If we don't like it, we can purge it overboard or use it for showering and laundry. Best of all, it keeps us actively watching where and how much the water is going into the different tanks.

The dedicated water pump was mounted under the galley sink on a bulkhead where the hose to feed the tanks could easily be stowed.

The long hose is able to reach all the tanks in the boat, even the tanks located under the V berth in the bow. The ball valve makes it easy to turn the water flow on or off to facilitate filling each tank to capacity without getting your hands in the tank. The pump can flow 4 gallons per minute at 60 psi. This would take 40 minutes to fill up all the tanks (160 gallons) at a fuel dock, but we anticipate that it will run much faster since there is no resistance in the system; hopefully decreasing the time we spend tied up to a pier as we refill our water supply.

The long hose tucks up neatly under the galley sink area, allowing us to carry this convenient length of hose without impinging on our daily life aboard.

The plumbing is complete, but we still need to power the pump. This is where my less favorite part of boat projects comes into play. As you may have noticed, I don't particularly care for electronic devices. Mechanical devices have all their parts on display while electrical devices have all their parts tucked away behind insulative barriers, hiding their corrosion and problems as you wonder why it's not working when you need it. 

Nonetheless, the water pump is electric and needs to be wired into the boats electrical system. This involves running a new positive and negative wire from the breaker panel down through all the inaccessible crevices to lead the wire to the pump. The first step is to open the panel up and start fishing wires through the backs of the interior joinery. 

While it may look like a spider web of wires, it actually isn't that confusing. All the positive (red) wires are on the left side, all the negative wires (black) are on the right side. It may be tempting to wire the negative onto another passing negative wire near the water pump, but this is not advisable. Each electrical component should have its own negative wire that runs back to a central negative buss bar.

Now that the pump is plumbed and wired, the rain water collection and distribution system can now be considered complete. All we have to do is wait for our next rain storm to give it a test!