Water Tank Scum

[gwilliman]

I am currently having a problem with "stuff" in my forward water tank on my SO419.  As I use it, the water clogs the small screen filter on my water pump for the sinks and showers. I am trying to add a small amount of bleach after pumping out most of the water and waiting to see if that will have any effect.  

I may decide to use a wet vac and empty the tank completely, rinse with some more fresh water and bleach, pump again, let dry and then refill.

Interested to know if anyone else has had similar issue and what recommendations there are for water treatment going forward.

Pictures below show the "stuff" floating around as I pump it out, and the "stuff" gathered on my pump that I used to quickly empty the tank.

   

www.23hq.com/23666/63173597_8d9812a9e25e0e01fdb972cb3e239dee_standard.jpg

www.23hq.com/23666/63173598_87f50c7aa8486bdca695a5184456f25e_standard.jpg

[Zanshin]

That looks like it is biological rather than chemical. Chlorine will kill it, but it will clog the filter so I think that you've got little options but to drain the tanks as far as possible and then mechanically remove what is left in the tank before re-filling it.

While I'm in the fortunate position of getting to use a watermaker for all my fresh water, when you fill your tanks just a couple of drops of chlorine and then waiting a day or two before using that tank will prevent future infestations.

Just a question - are your watertanks black plastic material? This is because algae won't grow in the absence of light.

[gwilliman]

The tank is blue plastic as shown in the picture, plus it is located underneath the forward V berth.  It doesn't see the light of day.

[Zanshin]

Then it would seem you got a bad batch of water! Could your filler cap be leaking a bit and you might have taken some green water into the tank while doing some sailing? That stuff isn't ancient as it still has some chlorophyll coloration.

[ForGrinsToo]

I agree - bleach is going to kill that stuff but it's then going to clog a downstream filter or - worse - a check valve. I am afraid you may be in for a removal and steam cleaning. I would nearly fill the tank, add maybe a half gallon of bleach, let it sit over night, pump it all out, fill with good water then pump out at least twice. Be sure to use only the cold water line and outlet (faucet) closest to the pressure pump. Or, as I might infer from the photo, use an auxiliary pump...

I also agree you probably got a bad batch of water, though you ought to check the o-ring on the filler plug.

I typically add 1 - 2 tablespoons (10 - 15 mL) of bleach on filling the tank (~175 L). If the taste of chlorine is too much, one can add a few ounces of drugstore hydrogen peroxide and convert the chlorine to chloride (aka table salt). I prefer to have the water tanks nearly empty when we're not aboard for more than a few days.

All that being said, I frequently get a white putty-like material out of the aft tank; it collects on the screen at the pressure pump. If it weren't so white, I'd suspect biological. But it's more like a fairing compound or sealing compound, a little bit tacky. The screen at the pump seems to do a good job.

Geoff

[davidfreedomsong]

There are lots of things you can clean with that are not going to kill you like bleach. You can put a cup per 2 or 3 gallons of water of hydrogen porixide, the %30 stuff and it will kill almost anything. let it sit for a few days and flush it with water, easy. You can add any amount of colloidal silver, I drink it straight daily, it is good for you and will kill all bacteria, molds, growths in most water is dealt with by just adding some silver to it in your tank. Again, use as much as you want, fill it, let it sit a few days and flush it out.

Bleach is not even supposed to touch your skin, don't ever drink any of it unless you are about to die in the amazon and need to make clean water on the spot. If you do drink any bleach it would be wise to start a kidney and liver flush right away. Bleach kills everything, even in small amounts....we are part of the everything it can kill. I don't even use it on my clothes, keep in mind....you can by cigarettes that are known to kill you also. To say the least bleach is not safe in any amount for human consumption. a large gulp, just one, will kill you.


www.quora.com/How-long-does-it-take-for-bleach-to-kill-you


www.answers.com/Q/Can_bleach_cause_cancer

[Zanshin]

Dec 3, 2019 22:13:27 GMT ForGrinsToo said:

I agree - bleach is going to kill that stuff but it's then going to clog a downstream filter or - worse - a check valve...

Bleach (sodium hypochlorite) chemically deteriorates very quickly and a thimbleful in the tank is more than enough to kill anything growing in there but after 24 hours you cannot even taste what hasn't decomposed already.

Considering that bleach is still commonly used to treat water in water plants it certainly won't kill anyone in those concentrations and authorities consider it harmless to humans. I think a better reference than a quora or answers.com article would be the wiki page at Sodium Hypochlorite and read the section on "Environmental Impact".

[rene460]

I am also inclined to think a bad batch of water as the source and would go for some bleach.  I would suggest emptying the tank with a portable pump of whatever type you have, then cleaning out the tank to remove as much as possible rather than pumping it through the system.  I think blocking filters and the valves in pumps is the main issue, such scum or similar floats around the edges of most drinking water sources such as dams and tanks, but usually filtered out in the treatment plants.  Probably not harmful if it came in with your drinking water supply, but most of us would rather not drink it.

There is not much choice but to get as much foreign material out of the tank as possible, then sterilise the tank and finally flush with clean water until clean.  Personally I would use bleach in the recommended concentration, but peroxide as suggested, or one of the proprietary tank sterilisers, if you prefer.  Don’t get bleach on good clothes, it removes the colour in the concentration used for bathroom cleaning, that is what bleach does. But for cleaning purposes the concentration used is much higher than used for drinking water sterilisation.  And I would wear rubber gloves, otherwise your hands will smell for a while.  But at the recommended concentration, it would be my choice.  Also, it’s not like you use it very often for such purposes.

The procedure I would then suggest once you have removed what you can and cleaned as well as possible, is some bleach or your other preferred drinking water steriliser at the recommended concentration for the tank size and after a day or so, empty it again again with the separate pump.  This should eliminate further growth.  Then fill and empty with clean water to remove any residual taste.  When a taste test is ok, try pumping through the cold water system, while keeping an eye on the pump inlet filter.  Clean it as often as necessary until it stays clean.

rene460

[ForGrinsToo]

First, Rene describes in considerably more detail essentially the same cleaning procedure that I suggested.

Zanshin notes that chlorination is by far the most common method for disinfection of potable water worldwide, with sodium hypochlorite (aka: bleach) being the most common agent. (Many water treatment facilities consider chlorine gas to be much too hazardous to deal with). The U.S. Centers for Disease Control says, "sodium hypochlorite appears to offer the best mix of low cost, ease of use, safety, and effectiveness in areas where there is enough water to drink and water is not excessively turbid."

Finally, the 1 or 2 tablespoons (~ 15 mL) bleach added to my 175 L tank works out to about 3 ppm free chlorine, which is approximately typical of a swimming pool. But it dissipates fairly quickly so that in a day or so it is at the 0.5 - 1 ppm level typical of drinking water supplies. As noted, that chemical process can be accelerated by adding a bit of household hydrogen peroxide (in case the Admiral is displeased). By itself, the typical 3% hydrogen peroxide is rather ineffective as a water treatment and is generally not recommended (https://iaspub.epa.gov/tdb/pages/treatment/treatmentOverview.do?treatmentProcessId=-1234021623).

Good luck, gwilliman.

Geoff

[Mistroma]

If your boat is currently stored ashore, I'd personally add a fair bit of cheap unthickened household bleach, fill the tank and leave for about 12 hours. You can empty the tank very easily by connecting a hose to a tap, taking it to the tank access cover and part filling a bucket (or put some in the tank if there's any space left). Put the hose to the bottom of the tank and then remove the hose fitting from the tap at ground level. The tank contents will gush out and the tank will empty as long as you keep the hose end close to the tank bottom.

I have shown this simple method to a few people who had been trying to pump out their tank. A simple syphon works well and fairly quickly with no need to supervise. It's easy to restart if the syphon stops, just connect to a water point, push air out and disconnect once enough water has run to fill the hose again.

Don't worry about too much bleach or the smell, you can flush a couple of times if needed. It's actually quite easy to direct a water jet inside the tank as the access port is fairly big. That will let you flush any residue from the top of the tank. I always keep some Sodium metabisulfite handy to kill off any excess bleach (ex. homebrewing/winemaking suppliers). Excess Sulfite tastes terrible and you can detect even a few parts per million (ppm) in water. Simply filling a tank with water will convert Sulfite to Sulfate and you won't even taste a few percent of Sulfate let alone a few ppm.

[Tafika II]

Both of our tanks have remained clean for over 11 years. Since we have a watermaker, we cannot introduce chlorine from city water or bleach into our system as it will destroy the membranes. We use an in-line hose carbon filter like the one pictured below with every water fill-up.