Purifying my water tank

[Kian]

I recently took ownership of a boat, and I wanted to make the water tanks safe for drinking water. Some details about the tanks: The boat has two plastic tanks, one forward and one aft. Forward tank is 330 liters, aft one is 200 liters. The water pump will not fully empty either, as by design the lower fifth of the tanks is used as ballast. So there's 530 liters, but effective tankage is about 400 liters (about 100 gallons). From what I've seen, the inspection hatches were never opened until I used them to pour in bleach.

Since I didn't know how the water had been sourced before, or how long it had been left standing, my approach was as follows: add 300 ml of bleach (with 5% chlorine) to the forward tank, 200 ml to the aft tank, fill them with safe water, then open the taps (in baths and galley) to empty the tanks as much as they will go. Then fill again and empty twice more, to lower the concentration of chlorine. By my calculations, by the third time it was emptied, the concentration should be safe to drink:

* 500 liters of water, 500 ml of 5% bleach: 0.005% chlorine
* Emptied down to 100 lt at 0.005%, then added 400 lt of clean water -> diluted to 0.001% chlorine.
* Emptied and refilled -> diluted to 0.0002%
* Emptied and refilled again -> diluted to 0.00004%

At this point, the chlorine should be down to about 4 parts per million, which I've read is a safe dosage. I've been using it for washing only, not drinking yet, and was wondering what other treatment would be recommended before considering the water safe to drink. There are a few filters along the circuit (before the pump, for example) but I don't know how much they filter. The water now comes out clear, no odd smell or taste.

Short of looking for a water inspection facility (which I don't know if there are any around me at this point), what other recommendations are there for checking the safety of the water? And for future maintenance?

I wanted to empty the tanks fully, but I didn't have suitable space for siphoning out the water or a portable water pump.

[GordMay]

Advice from the esteemed Peggie Hall:


Before beginning, turn off hot water heater at the breaker; do not turn it on again until the entire recommissioning is complete.

Icemakers should be left running to allow cleaning out of the water feed line; however the first two buckets of ice—the bucket generated during recommissioning and the first bucketful afterward--should be discarded.

1. Prepare a chlorine solution using one gallon of water and 1/4 cup (2 oz) Clorox or Purex household bleach (5% sodium Hypochlorite solution ). With tank empty, pour chlorine solution into tank. Use one gallon of solution for each 5 gallons of tank capacity. (Simpler way to calculate: 1 quart bleach/50 gal water tank capacity)

2. Complete filling of tank with fresh water. Open each faucet and drain cock until air has been released and the entire system is filled. Do not turn off the pump; it must remain on to keep the system pressurized and the solution in the lines

3. Allow to stand for at least three hours, but no longer than 24 hours.

4 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, because 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.

5. To remove excess chlorine taste or odor which might remain, prepare a solution of one quart white vinegar to five gallons water and allow this solution to agitate in tank for several days by vehicle motion.

6. Drain tank again through every faucet, and flush the lines again by fill the tank 1/4-1/2 full and again flushing with potable water.

An annual or semi-annual recommissioning according to the above directions is all that should be necessary to keep your water tasting and smelling as good as anything that comes out of any faucet on land. If you need to improve on that, install a water filter. Just remember that a filter is not a substitute for cleaning out the system, and that filters require regular inspection and cleaning or replacement.
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 certainly 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, because any harmful bacteria will REALLY proliferate in water hoses left sitting on the dock.

More here ➥ https://www.cruisersforum.com/forums...tml#post689753

[Peeew]

My boat is similar plumbing layout. Although my fresh water tanks seem clean and safe to drink from I want to keep them that way. Especially when traveling I fill with RO water from my Watermaker which means no chlorine or other antibacterial content. I add a small bit of bleach to each tank when filled and I added a filter to remove chlorine etc at the galley cold water tap. I think I’m keeping my tanks clean and have safe good tasting water to drink at the galley.

[tkeithlu]

Peggie Hall, as usual, has got it. Gord gets credited with an assist.

Kian, the only challenge I see in all this is agitating the water in the tank before flushing it through.

[Kian]

Well, those instructions seem pretty close to the ones I followed (after first placing the bleach in the tank I let it sit for four hours, forgot to mention that bit), so I'm relieved. Still, I will wait until I find a filter for the galley faucet before drinking. Even if everything in the water is dead, the dead microbes may still be floating there, and the filter may help with that. Or at least make me feel better.

Mostly because I can't fully empty the tanks until I get a small portable pump, so I'm only ever diluting whatever is in there but can't remove it all.

[Enialb2]

I found this overall plan helpful:
Sail Delmarva: Drinking Water Filtration--The Short Version

[Cadence]

I might open an inspection port, pass a hose down and pump out that ballast water. Then start with all fresh water and chlorine. Pump it all out several times then circulate it through you system several times. Bleach is cheap.

[thruska]

All great instructions and suggestions.
My tank is empty when it’s empty.
I need to run my hose in thru fwd hatch or trhu galley to fill. So its easy to flush and add bleach, flush , vinegar , flush, peroxide, flush n fill.
Peroxide kills more germs than anything else , and will not affect taste.
When dealing with these so called purifiers, note that they can neutralize one another in application.

[CarlF]

Your tank is clean. Now the trick is to have great tasting water so you don't have to lug bottles of water onto the boat.

The link above for Delmarva is what I do - including:

1. Get one of the Pentek Floplus filters he recommends connected to a water spigot at the sink.

2 Use a RV filter on the marina hose coming in.

3. Run the tank dry once a month and refill with fresh municipal water - its chlorine will keep the tank clean.

4. If the water ever has an "off" smell or you aren't regularly refilling with fresh municipal water - add Dichlor powder instead of bleach. Bleach loses its strength after 6 months in the bottle. A 2lb $20 container of Dichlor for hot tubs is fresh for 5+ years.

5. Use a test strip to get a municipal level of chlorine. I use 1/4 teaspoon of Dichlor per 100 gallons to get 1ppm - which you can't smell and can't taste but is plenty safe. I mix the 1/4 teaspoon in a quart container or water and then pour the right amount into the tank.

I never have any complaints for guests serving my tank water instead of bottled.

[Kd9truck]

I bought my Jeanneau SO 44i, 3 years ago after I came from charter service and neglect. The vessel was only 7 years old. If your tank needs to be cleaned, mine did, you should see what the lines/hoses look like. Put a filter under the galley sink.
I pulled the tanks and scrubbed them clean, I replaced all the hot and cold service and the thru-deck feeds. I also did the gray and black water hoses because previously in charter and other owners used bleach to “clean” the water and the utilities
As was described to me by the owner of a family Jeanneau dealership, there are 7 of them and they all have Jeanneaus. He said running bleach though hose for service, for gray water, for black water, removes the coating on all the hose but most importantly the black water hose. This creates permeation, permeation is the absorption of the black water contents into the hose that at the very least creates an unpleasant smell.
The dealer told me run the water, keep the water moving, his words, “Do Not Use Bleach!” He has a dealership and resources, he drains the system if he will be away for more than 2 weeks,1 gallon of white vinegar is what he pours into a full tank (100 Gal) to flush the system in the spring and that water never sees a holding tank (I have 3 heads, 1 is freash water, I highly recommend a freash water conversion).
I added a wash down spigot under the lazzerette that the transom shower service is located at and I rinse the deck of salt after almost every sail.
He said” keep the water moving, put a filter on the service under the sink”
Good luck

[more]

Originally Posted by Kian

I recently took ownership of a boat, and I wanted to make the water tanks safe for drinking water. Some details about the tanks: The boat has two plastic tanks, one forward and one aft. Forward tank is 330 liters, aft one is 200 liters. The water pump will not fully empty either, as by design the lower fifth of the tanks is used as ballast. So there's 530 liters, but effective tankage is about 400 liters (about 100 gallons). From what I've seen, the inspection hatches were never opened until I used them to pour in bleach.

Since I didn't know how the water had been sourced before, or how long it had been left standing, my approach was as follows: add 300 ml of bleach (with 5% chlorine) to the forward tank, 200 ml to the aft tank, fill them with safe water, then open the taps (in baths and galley) to empty the tanks as much as they will go. Then fill again and empty twice more, to lower the concentration of chlorine. By my calculations, by the third time it was emptied, the concentration should be safe to drink:

* 500 liters of water, 500 ml of 5% bleach: 0.005% chlorine
* Emptied down to 100 lt at 0.005%, then added 400 lt of clean water -> diluted to 0.001% chlorine.
* Emptied and refilled -> diluted to 0.0002%
* Emptied and refilled again -> diluted to 0.00004%

At this point, the chlorine should be down to about 4 parts per million, which I've read is a safe dosage. I've been using it for washing only, not drinking yet, and was wondering what other treatment would be recommended before considering the water safe to drink. There are a few filters along the circuit (before the pump, for example) but I don't know how much they filter. The water now comes out clear, no odd smell or taste.

Short of looking for a water inspection facility (which I don't know if there are any around me at this point), what other recommendations are there for checking the safety of the water? And for future maintenance?

I wanted to empty the tanks fully, but I didn't have suitable space for siphoning out the water or a portable water pump.

in Croatia is easy task I go to farmacy and order CAS no 2893-78-9
https://en.wikipedia.org/wiki/Sodium...roisocyanurate
At begining season put 3x dose wait 30-60.minute and after this with this water I use to wash boat outside ,inside ,toilet tank all boat when tank is finish,put new water and you are ready.also use Liquid Dish Detergent/soap with Sodium_dichloroisocyanurate for washing dish,flor,toilet.hospital use water and Sodium_dichloroisocyanurate for wash shets from all known viruse and bacteria /except ebola,maburg i think.cheap,safe easy

[thruska]

Originally Posted by thruska

All great instructions and suggestions.
My tank is empty when it’s empty.
I need to run my hose in thru fwd hatch or trhu galley to fill. So its easy to flush and add bleach, flush , vinegar , flush, peroxide, flush n fill.
Peroxide kills more germs than anything else , and will not affect taste.
When dealing with these so called purifiers, note that they can neutralize one another in application.

Get a Camco rv carbon (charcoal) filter, use it on the end of the hose closest to your tank fill. Amazon has them for around 14$.

[David B]

Originally Posted by Kian

Well, those instructions seem pretty close to the ones I followed (after first placing the bleach in the tank I let it sit for four hours, forgot to mention that bit), so I'm relieved. Still, I will wait until I find a filter for the galley faucet before drinking. Even if everything in the water is dead, the dead microbes may still be floating there, and the filter may help with that. Or at least make me feel better.

Mostly because I can't fully empty the tanks until I get a small portable pump, so I'm only ever diluting whatever is in there but can't remove it all.

You might like to install a Seagull filter system. They are excellent (and used on commercial aircraft). Remove taste and pathogens. The cartridges are not cheap, but they last (for us, using the boat 2-3 months a year, for two people, one cartridge lasts 3+ years).

[LittleWing77]

Just buy Peggie's book and read it from cover to cover:
The New Get Rid of Boat Odors
https://shop.sailboatowners.com/prod.php?53615/

Good luck!
LittleWing77