Some of you may have seen a few of my posts, but a little background to start this conversation is required. I am a mechanical engineer
, with a background in software
development. I am turning 30 now and have just started my professional career after long delays of education, life and debt. I want to start my professional life living on a boat and using it to move from job to job taking advantage of the coasts.
In pursuit of this ideal, I have realized this: The cost barrier to entry is way to damn high for cruising. Not the boat, there's plenty of cheap
plastic boats for anyone willing to put the sweat into getting it sea worthy, rather every other cost is high.
Part of my goal, as an engineer
, and a man on a limited budget
is to bring those costs down. My first target is water
. Its absolutely essential and a ready supply at low to no costs (I can imagine) makes all the difference living aboard
Most systems I have seen run in the ball park of $2500 to $3500. In researching RO filters and the system requirements, I believe this to be whole heartedly over priced.
I intended to build a system and I would like to sell it in the future. My price
point objective is $1000 to $1500. I intend to construct with components and parts
readily available through commercial
suppliers (McMaster Carr) and to use low cost electronics
that are viable, capable and replaced at low costs as well as fully rebuildable at sea.
To accomplish this, I have several perspectives that I would like to vett with the community.They are listed below. I would like to hear input back from the community.
1. 150 PSI RO filters.
Currently, I see these types of filters priced in the $80 range with housings around the same prices. Their capacity far exceeds demand (125GPD) and waste water
rate is around 5:1. Has anyone used these or had failures with them?
2. Non food
grade water pumps.
I know this sounds nutty, but the water is hitting a RO filter, you could run the water through an oil
lubricated pump and not have a problem. It raises the issue of contamination due to filter failure though, which I will address next. This is a primary cost saver.
3. contamination detection
Two methods will be used for this, conductivity readings and pressure faults. Using a secondary tank, all clean water will find its way here first. Conductivity will be checked and the software
will test this before allowing the low pressure discharge pump (food grade) to move the water to the holding tank
There will be a light check valve on the clean water output, this will allow a pressure gradient post filter. This pressure gradient from input pressure to output pressure will indicate the health
of the filter. A increase in gradient indicates filter clogging, a decrease in gradient (severe) indicates a filter failure.
The conductivity test and the filter failure test will shut the system down and prevent pump out to the primary holding tank
4. Non self priming high pressure pump.
pre pump, post pump system.
There will be a small pre tank and post tank. Pre tank will have a low cost, low pressure pump capable of self priming and pumping to the pre-filter then to the pre-tank. This allows a non self priming pump to be used, which has a much lower cost. Pressure gradients across the pre-pump will be again used to check for pump and filter failure as well as prevent run-dry on the high pressure pump.
5. Arduino Logic controller -
These little buggers are cheap
, but come as a raw board. I can most likely get a system with enough inputs and outputs to run this on and the requried sensors for under a $125. The boards can be replaced completely for $65 and the controller logic chip for under $20. This will require a sealed dry box for the electronics
to protect them from the elements.
6. Recommended secondary water tank
My recommendation would be a primary fresh water tank
and secondary freshwater. The secondary could be 10-15 gallons. The system should be able to supply 150 gpd, roughly 6 gph. The secondary tank could be rigged with water level sensors and the system could be setup to run automatically for a low cost. This would allow the user to fill their primary tank manually and then run high consumption
devices (e.g. shower) off of the secondary. This would provide the safety
net between the primary and secondary water tanks
The goal is $1200 for a final product to a customer (Us!).
Complete electronics rebuild
Complete pump rebuilds for $250
Full Filter replacement, $120 (RO:$80 pre-filters $40)
I want anyone with a screw driver to be able to rebuild