fresh water capacity - brunnhilde part 9

The Comet pump parts finally arrived from UK via Royal Mail. It arrives faster (about 5 days) than my Sub-Prime orders from Amazon because Amazon wants me to pay them the Prime annual fee. For free shipping on qualified items that totals at or above $35, Amazon now holds the shipment until the very last days knowing the USPS Priority mail they use will get the package to me in just 3 days, instead of what Amazon's ETA of 10 to twelve days. I have observed this many times now.

These are the last parts to complete the convertible auxiliary water tank project.

While I order two pumps and two non-return valves, I only need one of each so the other are spares.

draining the water to swap in the Comet VIP Plus pump and the non-return valve

I slipped the non-return valve on top of the Comet VIP Plus pump. It was a bit of struggle to swapped out the cheap Chinese made pump that I temporarily installed because the hose clinss tenaciously to the barb fitting of the Colder panel mount connector. Remember I have to reach in through the access port made with a 4-inch deck plate and with one hand it is a struggle to disconnect a PVC hose from a plastic barb fitting. The stacked height of the VIP Plus pump and the non-return valve is considerable, leaving only about 2 inches of space for a hose stub between the pump/valve and the Colder connector. I cut the hose slightly long so it keeps the pump tightly against the bottom of the tank.

these pumps are clearly marked "Made in Germany"

I soldered up the pump cable to a mic plug and proceed to test the fresh water system to ensure it functions as I designed. The three position rocker switch is the only thing one have to use to choose which tank to consume. It is simply Primary - Off - Auxiliary. Both pumps deliver adequate pressure for the shower, which is the worst case task for the pumps. There is no discernible difference between all cold and all hot. The non-return valves are doing their job of preventing water being pumped from one tank to the other.

On the rest of the tank's pumbing, I revised the fittings used for the filling/draining port to reduce the cost, and improve the functionalities. The final version uses common 1/2 PVC plastic valve instead of the expensive Gardena valve. The PVC plastic valve is a better choice as it is much stiffer to turn - no accidental turning. I also increase the hose ID to 1/2 with the use of a clear PVC hose for better visibility. I increased the length to make it more stowable. The overfill/breather hose now sports the Colder connectors as the cutout in the sheet metal shroud that protects the wires and plumbing does barely provides just enough clearance for them. Every aspect of the new tank system is a tight fit and often with just millimeters of clearance.

In this project, I looked at countless plumbing fittings at Home Depot and West Marine, and those from Colder Product Company. I now know Home Depot's offering better than most plumbing department staff there. In the process, I discover a few nice fittings that I previously unaware, like the PVC schedule 40 to garden hose threads. Also I refuse to succumb to big box store's line item reduction that forces you to buy a few fittings when the right one does the same job (these big box store only carry a subset of the available fittings - to take schedule 40 PVC fittings as an example).

the longer fill/drain hose is easier to stow securely - counter intuitive; it also work much better when draining the tank

 here I am filling the tank

As designed, the auxiliary tank can be installed or removed without any tool. It can be done in less then 3 minutes. In trips that more cargo space is desired the auxiliary tank can be left at home. There is no need to manually plug the hose as the Colder valved connector handles it nicely and securely.

When carrying both tank, it is preferred to consume the auxiliary one first to reduce the vehicle's center of gravity.

When I was designing the auxiliary tank, I went through countless different design ideas. Many were summarily rejected. Few that were retained went through many steps of refinements as I considered cost versus benefit tradeoffs, the usability and reliability, and cost and complexity reductions.

As Apple like to tout, there many many more no's than yes's. It is important to say no to most idea that first came to mind, and say yes to the few refined and distilled. I also was able to minimize the number of openings on the water tank by using the drain port to double as fill port also (note that the tank can be gravity fill via the service port).

To list a few of the rejected ideas:

• Provision a filling port by repurposing one of the defunct utility ports
• Use of a diversion valve to select which tank to consume from
• Transfer the water from one pump to the other to avoid the need for a design to select which tank to draw water from
• Add a level sensor to the auxiliary tank
• Work harder to shoehone in the bigger 15 gallon tank instead of the 13-gallon one