Ever experience one of those pesky problems that you just can’t seem to find the solution for? We kept getting a “positive for coliform” reading on our product water test from our onboard water maker. We solved the problem, but not without much frustration and a cramp in the wallet. Read on for the whole story.
We consider our water maker to be a critical system (for us) given the kind of cruising we do. We will spend much more time at anchor than at the dock (as most do) in the Caribbean so our water maker is important to us. We shower aboard (daily) in two full sized heads and we have a 180 gal onboard fresh water tank. We use a lot of fresh water – our water maker needs to be at the top of its game.
We have an SK water maker. A big one (60 gph). It was pickled (placed in a storage state) for several years. We revived it now that we are cruising. Since purchasing our boat, the water maker is now nearly new. We had the high pressure pump rebuilt a few years ago by the manufacturer.
We just replaced the pressure vessels that hold the membranes. We put in new membranes last month. We keep the pre-filters fresh and only make water from outside the marina. After three BAC-Ts, we were still reading that coliform is present in the product Water. This post is about what we did to resolve this issue.
Let’s start with some background. First, we were not drinking the product water nor have we diverted any product to our tanks – and we won’t until We see a ” negative” BAC-T (Bacterial Test for coliform). Our system is a Reverse Osmosis (RO) unit consisting of a GP Companies 220V high pressure pump model CC3615CL. The pressure vessels (a pair of them) are from Composite Concepts and the plumbing is packaged as a system with these major components by SK Watermakers. We have a two-pack pre-filter set with a 30 and 5 micron cartridge and a pickling/flushing switch bank. The operator (that’s me – Steve) has a military background in water purification from the Army – so I know the principals of RO better than the average guy. Nonetheless, I had significant issues solving our presence (positive) of coliform problem.
Bottom line up front – We solved the problem – we had a number of issues, when combined, that were causing dirty product water. Here’s what we did to diagnose and fix it:
– Un-pickle and flush: We evacuated all of the pickling solution from the system and flushed with source water (do not use tap or dock water with chlorine). We then changed the pre-filters and cleaned all of the filter vessels and ran the unit in production mode for 30 minutes. After testing Total Desolved Solids(TDS), we then cleaned the milipour port with alcohol and took a sample for the BAC-T.
– BAC-T positive #1: As a result of the first “positive” BAC-T, we de-scaled the system with a low PH acid cleaner from SK called CH-751. This is supposed to clean the membranes of deposits. It didn’t work, so we replaced the membranes at around $400 and retested.
– BAC-T positive #2: The second test was positive for coliform and I determined that one of our pressure vessels had a crack that was leaking so we replaced the pressure vessels and installed the new membranes in them. We also replaced the pre-filters. We drew another BAC-T.
– BAC-T positive # 3: The third test was still positive for coliform. By this time, I was pretty frustrated. I reviewed the installation of the pressure vessels and realized I had a set of pressure hoses reversed from installing the new equipment that had a slightly different flow routing path than original – fixed that. We removed the product hose and chlorinated it to the sample port. We also treated the entire system with SK’s CH-752 high PH Alkaline Cleaner. We then drew another test.
– Success!…BAC-T NEGATIVE: Finally!…a “Negative” result-No Coliform! We are in business!
Reflecting upon our struggle to ensure our drinking water remains safe, our detective work helped us conclude that our problem was a combination (or cascade) of deficiencies:
– Cracked pressure vessel (replaced with 2 new ones)
– Misrouted hoses (my improper installation)
– Old stuff growing in the product output lines that the cleaning solution never flushed due to the aforementioned misrouted hoses
It’s a BIG load off of our minds that the water maker is good to go! The negative BAC-T photo is living proof! Nothing floating at the top of the vail is good news after 48 hrs! To keep it in shape we will run it every 3 days for 30 mins until we are making water for our Caribbean crossing in December, after which it will likely be run daily.
This was the last major system we needed to have up and running at full speed for our transition from the US East coast to the Caribbean. As we migrate further South along the Florida coast, the water will get clearer, the weather warmer and our excitement grows as we move on to the next milestone in our adventure.