Leaving bleach in fresh water tank during the winter.

[JimDarla]

I see the posts for sanitizing the fresh water tank, but I was wondering if there is a problem leaving the i/2 cup of bleach in the full fresh water tank over the winter. We live in Florida in the winter and the AS is in storage for approximately 6 months. I am concerned mold may start growing in the tank or lines if it is fresh water only. Thank you.

[A W Warn]

Clorox says " Under normal usage, it will quickly break down to 95–98% salt and water, and any remaining bleach will quickly react with components in your sewer or septic tank line."
IMO, there is no benefit to leaving it long term. I think getting the tank drained completely is a better strategy.

[ROBERT CROSS]

I don't think it's really needed in a dry tank, but in Florida, certainly doable.
I wouldn't do it because of the possible damage to the dump seal from extended bleach exposure.
We sanitize every Spring, 1/3 cup in full tank for 24hrs.

Bob
🇺🇸

[BayouBiker]

It's not a great idea to leave bleach in the tank longer than required to do its job. The reactions do break down to salts and it will continue to react with and oxidize the proteins and oils so over time it will loose strength anyway. It will be just a touch harsher on some of the less resistant components with little added benefit, and it can be just a bit harder to rinse all the residual out.

Mold can only grow if there are nutrients. A bleach soak with the tank full will kill the mold spores etc. A good rinse with very fresh water and then emptying the tanks will deny nutrients so a new colony can't start. I suppose if your rinse water is questionable this strategy will not work so well.

[majorairhead]

I would drain the tank, fill it in spring with a wee bit of bleach.

I'm on town water, can smell when they chlorinate, never worry about bleaching the system.

[telcoman]

yes drain it. Put a couple of capfulls in when you refill, drive it around and drain it again. blow out the lines

[banderabob]

Drain it so it dries out, we leave the drain, low water points and hot water heater tank all open when winterized.

[Ken G]

The chlorine will evaporate. The warmer it is the quicker it will evaporate just as it does in your pool or spa. Also strong concentrations of chlorine are corrosive as it is as oxidizer but I’m not sure if it would contact many metal parts in the water tank.

[fthopkins]

Full disclosure, I don't know the science but here's what I do: On my last trip of the season after unpacking at the house, I open the fresh water tank drain. Then drive (tow) my RV roughly 25 miles to it's summer home (we do our traveling in the fall, winter and spring). When I park it, I close the drain (to keep the mud dubbers and other undesirables out). Then on the first fall trip, I pour a cup of bleach in the tank with 5 to 10 gallons of water in it. Pump some water into all the piping then drive back to the house, letting the water do a good slosh job. Then while packing for the first trip, I let the bleach water drain and give it (and the lines) a good flushing.


BTW, I hope I'm not hurting my black water tank, but on my first trip of the season I put a cup of CLR along with 5 gallons of water. Then drain the tank upon arrival out at our first camp site. Long story why I do this, Has something to do with buying a RV that had been parked for years before I bought it. I sure won't object of someone tell me to stop doing that or to keep doing that or describe a better way.

[jaybauman]

If there is nothing in the tank for the bleach to actively oxidize, it will decompose on its own. The warmer the temperature, the quicker the decomposition. If you keep the initial concentration within the recommended levels, you won't have any problems.

If you put a high concentration into your tank and leave it there, you have some minimal risk of degrading seals.

[JCWDCW]

As several others have reported ... don’t do it.
The active component in bleach is free chlorine
It either gets consumed by reacting with contaminates or it eventually evaporates. What is left is sodium hydroxide ( lye for us old enough to remember ) caustic soda is not good for rubber Seals.
There is no benefit and lots of downside from leaving bleach longer than necessary to sanitize. Empty the tank

JCW

[telcoman]

One other thing from experience. Our company runs RV Caravnas (including Airstream) to Mexico. (See the airstream club site if they interest you.) We advise people buy bottled water down there and just use the fresh water tank for showers and dishes & toilet flushing. Now the water is not drinkable in most places, so we advise people that when they cross back into the US, they drain the fresh water tank, put in 1/4 cup of bleach (that's a lot) fill the tank and run the taps for a minute including the shower. By then you should be down 1/4. Then drive it for a couple of hours so it sloshes around and has time to kill any bacteria or mold. Empty and refill, run the taps, run the hot water longer to flush out that tank. Drain again and refill again. After that you should be fine and safe to drink out of it. If it still tasets of chlorine drain and fill again.I have got into the habit of never drinking out of my RV tank anyway. I have gotten so use to using bottled water for drinking. BTW make sure you drain the black & grey tanks first. Bleach can react with some sanitizers. so you will also want to drain it again beofre adding any more.

[suncoasteng]

Originally Posted by BayouBiker

It's not a great idea to leave bleach in the tank longer than required to do its job. .

Bleach is an oxidant. Its strength will drop based on temperature and time. Laundry bleach is a lower strength that Pool bleach, but both decompose rapidly once "out of the bottle" It may, or may not damage your tank, depending upon what the tank is made of. You might also alternate and use ammonia to stop growth in your tanks. In a perfect world, you put fresh water in your tanks, use it up and refill the tank every week. Now, if you do not use the water every week, is it better to drain the tank, or keep the tank filled with clean, chlorinated water??

Depends- what is the tank material - aluminum, plastic, HDPE, fiberglass, steel? Be careful using too much bleach (CL2) with steel and alum tanks. HDPE -pour in a gallon of bleach and drain it out in 3 months with not problems.

I have always found that keeping a tank full of water, or fuel, works best. Unless of course you have freezing temperatures. If freeze is an issue, dose with high chlorine, then drain and store empty. Oh, and plug all vent lines so the wasps do not move in. Then just fill, high dose and flush in the spring.

If no freeze, keep tank full and maintain a residual chlorine level by adding a few cups of laundry chlorine once a month.

Your local city water system adds CL2 continuously to maintain the residual level so nothing grows on the walls of the pipes and hot water tanks.

[Wheelshed]

Bleach quickly evaporates into the air if left in an open pail in just 24 hours. Not sure how long it will last in a vented tank but probably not long.

Better to use distilled water it never gets funky if you want to leave water in there.

[BayouBiker]

The tank vent is very small and long, and there is no circulation when not in use. The bleach would have to defuse from the tank. It will likely remain for weeks at least. Leave it in if you want, it will likely do little to no harm but it is not the best option.

[glenrms]

And a quick note about bleach... It has a limited shelf life and will start breaking down about 6 months from manufacture date.

[JCWDCW]

Originally Posted by Wheelshed

Bleach quickly evaporates into the air if left in an open pail in just 24 hours. Not sure how long it will last in a vented tank but probably not long.

Better to use distilled water it never gets funky if you want to leave water in there.

It’s not the water but the contamination from air, left over residue and many other sources so distilled water is not a guarantee

It doesn’t take much chlorine to keep lines clean. City water is fed out to the distribution network at 1 ppm but they still do a high dose purge at night which is why you sometimes smell chlorine in morning tap water. Bacteria still grow in sterile water unless there is something present to kill them
JCW

[napabill]

It shouldn't hurt anything. In fact plain, unsceted bleach can be used to purify drinking water, just like the chlorine added to municipal water supplies. It may not smell nice but it won't hurt you in the proper dilution. The EPA and other bodies suggest 8 drops of bleach to a gallon of water, quite a bit less than used to sanitize your tank (1/4 cup per sixteen gallons of water.)
https://www.epa.gov/ground-water-and...drinking-water

[Wross]

The problem is the Stainless Steel, the pump, the filter, etc. The poly tank should not be affected, bit the seals and the pump, fixtures are degraded by the chlorine. Use it and dump it, don't leave it in contact with your plumbing, and at all costs, DONT Spill it on the Aluminum!