I have a Spectra Catalina
with an MPC-3000 controller, installed in 2005.
The watermaker’s salinity has been going up the past couple of years, along with corresponding decrease in feed water
pressure. Original salinity was 150 PPM, then gradually went up to 400 PPM range, and this year it finally got to the point of salinity greater than 750 PPM which is the maximum acceptable value in the control system (all water
, none to the tank). Feed water pressure was originally 95-100 PSI, but now is down to 82 PSI.
The problem was that I have been using propylene glycol to pickle the system during Mexico
summer lay-up time periods, per Spectra’s instructions. I used PG instead of Spectra’s SC-1 storage
solution because lay-up time was up to 8 months; Spectra says SC-1 is only good for 6 months, but that PG is good for a year.
Well, the Spectra Roving Rep here in Barra de Navidad, Mexico
, informed me that PG can contain alcohol, which is death to the membrane. I looked at one of my bottles of PG, Camco Arctic Ban RV Antifreeze
(-50 degrees F), and sure enough it says “Contains Ethyl Alcohol 64-17-5.” Ouch.
Spectra factory said that this killed my membrane by causing larger openings in it, which both reduces the pressure and increases the salinity.
I’m getting by this season by resetting the maximum acceptable salinity to 800 PPM, since the system gets it down to the 750-800 PPM range and thus delivers water to the tank. I’ve been told that the US Navy
considers 800 PPM salinity to be acceptable, and the World Health
Organization has a threshold of 1000 PPM. I’ll bring a new membrane down next season.
Be very careful out there if you are using PG for pickling. Make sure it does not contain alcohol.
I’m looking for a source of propylene glycol that does not contain alcohol, and is preferably rated for minus-100 degrees F as recommended by Spectra. Any words of wisdom as to source for this would be appreciated.