1997: Design: Pressure Water System


Adagio’s pressure water system is fairly straightforward — though we have not seen some of our design solutions — such as our hot water loopback scheme on any other boats. As the schematic shows [click the thumbnail] it only takes three valves and a bit more pipe. The valves are situated each of the places you will want hot water — when opened the valve simply routes the hot supply back to the starboard tank. Thus, you can have hot water “immediately” without pumping precious fresh water down the drain while waiting for the hot.

Other design features we appreciate:

Triple parallel pressure pumps

As the schematic shows, the primary pump manifold is comprised of parallel Shurflo 2088 Baitmaster pumps. These are controlled by external heavy duty pressure switches set for staggered on pressure trips:

Pump#1 controlled by — HI switch: 25 psi on, 42 psi off.

Pump#2 controlled by — LO switch: 15 psi on, 42 psi off.

Normal conservative use only activates Pump#1. But if we have guests aboard –> simultaneous showers, then Pump#2 will double the supply volume.

The external pressure switches eliminate the most commonly reported failure mode — internal pressure switch failure.

Live Redundancy

The other big benefit, as for all or our parallel pumping systems, is that if either pump fails we still have pressure water until we get around to fixing the fault — which will hopefully not be at sea.

In this design, we went one step further to achieve triple redundancy. The Port -> Starboard transfer pump is another Shurflo 2088 Baitmaster. The port-side 3-way valve shown is normally set to connect the port tank to the pressure water main line. So if we have a glitch with the main pump manifold {like a suction-side air leak} we can just turn on the transfer pump, turn off the main pumps –> fresh water service continues.

5-way Redundancy

We strive to use the same pump model everywhere it makes sense. Then in the extreme case we can just “borrow” the same pump type from another use. In this case, our salt-water washdown pump is #4 Shurflo 2088 Baitmaster. And #5 is stored in our spares inventory — and sometimes used as a utility pump.

The Plumbing

We originally planned to use the Whale Quick Connect Plumbing System. On our builder’s recommendation we elected to use a NZ-made household-standard polybutylene plumbing system. Allan has used this system for some twenty years now — never a leak or fault. A critical detail — all the connections should be crimped using a serious professional crimp tool.

If you Google “polybutylene plumbing” you will discover the power of the tort lawyers in America. I understand there was a problem decades ago with a particular USA vendor supply defective pipe — even today the free-lunch continues.

It has been a good choice for us — 100% reliable so far.

If you are retrofitting an existing boat I would probably choose something similar to the Whale system. Unlike polybutylene it is flexible and easy to modify.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s