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Flushing/testing/preping an old water system on a new old boat

6K views 8 replies 6 participants last post by  sailaway21 
#1 ·
I have no idea what the history of the water tank is on my new/old boat. Is the general procedure the same as a trailer or common sense would tell you. Anything special about a boat I need to look for? I get the sense the system was largely unused for the last couple of owners, but I plan on some short cruising and overnight gunkholing on the hook so need it.
 
#2 ·
Yup... shock treat the whole fresh water system... then flush it out a few times. Put some vinegar into it after the shock treatment has been flushed to get rid of any nasty residual odors or tastes... and then rinse a couple more times. :D

Before you shock treat though, you should check the hoses. If they're coated in gunk, it would probably be wise to install new hoses after shock treating the system. No sense in getting the gunk in the new hoses. Most FW systems use a clear hose, and if it is black, or grey with gunk... ditch them. If you're really worried, might be worth replacing the FW faucet fixtures too.
 
#5 ·
Mike/Pmoyer-

Shock treating a water system is essentially just running a solution of chlorine bleach and water through the system to kill off any residents of the water tank and hoses. The concentration of bleach to water doesn't have to be really high to be effective. According to Peggy Hall, the water and waste guru of boating, this is her recommendation:

Fresh water system problems--foul odor or taste--are typically caused by allowing water to stagnate in the tank and especially the lines, creating the ideal environment for molds, fungi and bacteria that thrive in damp dark places. Here's the recommended method for recommissioning fresh water systems; this should be done at least annually:

Fill the water tank with a solution of 1 cup (8 oz) of household bleach per 10 gallon tank capacity. Turn on every faucet on the boat (including a deck wash if you have one), and allow the water to run until what's coming out smells strongly of bleach. Turn off the faucets, but leave the system pressurized so the solution remains in the lines.

Let stand overnight-- at least 8 hours--but NO LONGER THAN 24 hours. Drain through every faucet on the boat (and if you haven't done this in a while, it's a good idea to remove any diffusion screens from the faucets, 'cuz what's likely to come out will clog them). Fill the tank again with fresh water only, drain again through every faucet on the boat, repeating till the water runs clean and smells and tastes clean.

Cleaning out the tank addresses only the least of the problem...most of the problem occurs in the lines, so it's very important to leave the system pressurized while the bleach solution is in the tank to keep the solution in the lines too.

People have expressed concern about using this method to recommission aluminum tanks. While bleach (chlorine) IS corrosive, the effect of an annual or semi-annual "shock treatment" is negligible compared to the cumulative effect of holding chlorinated city water in the tank for years. Nevertheless, it's a good idea to mix the total amount of bleach in a few gallons of water before putting it into either a stainless or aluminum tank.

To keep the water system cleaner longer, use your fresh water...keep water flowing through system. The molds, fungi, and bacteria only start to grow in hoses that aren't being used. Before filling the tank each time, always let the dock water run for at least 15 minutes first...the same critters that like the lines on your boat LOVE the dock supply line and your hose that sit in the warm sun, and you don't want to transfer water that's been sitting in the dock supply line to your boat's system. So let the water run long enough to flush out all the water that's been standing in them so that what goes into your boat is coming straight from the water main.

Finally, while the molds, fungi and bacteria in onboard water systems here in the US may not be pleasant, we're dealing only with aesthetics...water purity isn't an issue here--or in most developed nations...the water supply has already been purified (unless you're using well-water). However, when cruising out of the country, it's a good idea to know what you're putting in your tanks...and if you're in any doubt, boil all water that's to be drunk or used to wash dishes, and/or treat each tankful to purify. It's even more important in these areas to let the water run before putting it in the tank--wash the boat, whatever it takes...'cuz any harmful bacteria will REALLY proliferate in water hoses left sitting on the dock.
I hope this helps. :D
 
#6 ·
SD - Thanks so much. That's a wonderful description of what needs to be done. I unpleasantly discovered, though, that my new old boat has built-in water tanks, and the PO (or, more scary, maybe the PO before him) filled the tanks and left them that way. I had a very tough time getting the tank fill valves off (not on deck - they're on top of the tanks). They have a slimy green corrosion-looking stuff on them. When I peered down into the tanks with a light, I saw nasty grey water.

I'm not sure how functional the FW system is. I expect I need to replace the manual pumps, fixtures, and definitely the hose (it's all yellowed and crudy looking). But, I need to get the water overboard. I'm thinking about sticking a manual bilge pump into the fill hole and manually pumping the nasty water out of the tank into a bucket so I can dump it.

Once I get the tanks empty, will the above process be sufficient to clean them out, or do I need to take some more drastic steps? I'm worried that there's going to be an inch of toxic waste on the insides of the tanks....

Cheers!
 
#7 ·
Ive got this same thing coming up on my own boat. My boat used to have a 30 gallon tank on each side under the settee, but one was cut out of the boat. Ive got one 30 gallon tank under the starboard settee and an 11 gallon tank in one of the cockpit lockers. I only use the 11 gallon tank since i got it new and its clean. As for the under settee tank its fairly clean, but not clean enough. Im going to scrap all the lines on the boat and replumb it soon. Ive got 2 foot pumps i plan on useing since we're heading out on anchor. I dont know if i want to put a salt water pump to the galley since the water around here isnt that clean. Ive got another 11 gallon tank that im going to install somewhere in the boat.
 
#8 ·
Pmoyer-

Glad to help. :D I would recommend you shock treat the water system, flush it with fresh water several times, then change out the hoses, and then re-shock treat the water system, and flush again. Then do a final flush with some vinegar, to help get rid of the chlorine aftertaste.

SVDS- This same treatment might help with your 30 gallon tank and make the water useable for non-potable uses.
 
#9 ·
This is an area I know quite well as I frequently treat wells and houses for bacteria in the water lines. The bacteria is very rarely from the well; it usually originates in the house and grows through the lines. As mentioned, standing water is the culprit. In the case of most homes, running out all the garden hoses and letting them run for three days usually flushes out the bacteria and no chlorination is necessary.

In the case of tankage, especially in cases where the bacteria has had time to grow, sterner measures are necessary. If possible, circulation of water through the tank, and water supply system, is highly desirable. The effectiveness of chlorine, and bleach is the most effective form of chlorine, is dependent upon pH. The water solution should be slightly acidic. Most water available will be alkaline or pH neutral. Acidic water is not very common. You can test with a pH strip or just wing it. Before introducing the bleach solution to the tank, adjust the pH of the water to make it slightly acidic. Vinegar, in the proportion of 1 gallon per 100 gallons of water is usually sufficient to do this. Once the vinegar is mixed thoroughly with the water, bleach, at 1 gallon per 100 gallons, can be introduced. Use ordinary bleach with no additives. Do not use swimming pool shock or similar products. Those products are calcium based and will move the pH upwards into the alkaline range and reduce it's effectiveness.

Realize that you may have to treat the tank more than once. this is where circulation becomes important. Ideally, treat the tank and then pump it through all lines, returning to the tank. Recirculate for a few hours, pump to waste, re-treat, and let stand as long as practicable. The longer the contact time the better the results. Circulation, and repeated chlorination, are desirable in bad cases because the nature of the bacteria is that it grows in colonies, one atop another. You may kill the outer colony, and, if too strong a chlorine solution is used, this will inhibit the penetration of the sanitizing solution to colonies beneath. Repeated treatments, in the sanitizing proportion described, are more effective than one shock dosage. Again, circulation is highly desirable.

If your tank has crud, schmutz, or dirt in it; it is important to get that out prior to chlorinating. These will really eat up your sanitizing solution in a hurry, and until removal, may make it impossible to kill the bacteria. One other item, not commonly found on boats, should maybe be mentioned. If you have any "dead end" plumbing it should be removed or opened up and allowed to flush. Pipes that hold standing water, that does not circulate, are havens for bacteria.

I would not be concerned about aluminum or stainless steel in the concentrations mentioned. The chlorine will neutralize itself fairly quickly, and flushing out too soon, losing contact time, is much more of an issue than any potential etching that could possibly occur. This is another reason to not use swimming pool shock and the like. Chlorine in those concentrations is a strong oxidizer.

If you want to be more scientific about it all, you can pick up a hot-tub/pool bottle of tests strips which will test for pH and chlorine. Cheap and easy to use. Furthermore, after completion you can fill your tank, let it sit for a few days, draw a water sample and have your local health dept. test it for coliform bacteria. Test runs about ten bucks and they have special collection bottles. Follow the instructions very carefully as the test is highly sensitive. If you have the slightest bacteria, say on the exterior of the faucet you are drawing from it can result in a positive test, even though the water in your lines may be fine. Or you can do it the "Dutch" way and just drink the water for a few days, and if you don't get the green apple two-step you're probably just fine.

One other method of treatment is highly effective, but may be impractical. Bacteria dies off in hot water. If you can get hot water circulation, above 150 degrees F, through the system you will kill it off. This is more difficult than it may seem. You need to keep the water temp above 150 degrees during the circulation period. In a large tank, it may be difficult to have enough supply of hot water.

Lastly, there is no substitute for circulation. Prolonged flushing will do more than anything else to clean up your system.
 
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