Dirty water tanks

[lockwood]

The water tanks on my 22 footer have been unused since I bought her last year. I pumped some water through today and it cam out brown - with crawlies & wildlife floating!

There is no drainage point on the tank, just the tap and an inlet.

I will be pumping the old water out and flushing through new water until it runs clear then using some sterilisation tablets. Anybody know any ways of further purification? I would try bleach but my throat tends to disagree with it!

 

[Cobra25]

Milton is supposed to be good read instructions but I would only use for washing up water from that tank now

 

[pvb]

Bleach is actually the right stuff to use...

Sodium hypochlorite (bleach) is an excellent way of removing contamination in water tanks. People will suggest you use Milton, but that's basically only very expensive, watered-down bleach, so ignore their advice. Ordinary household bleach is typically 5% sodium hypochlorite; from memory, Milton is 1% sodium hypochlorite.

Start by rinsing the tank with a superchlorinated solution, this needs 10ml of household bleach per 10 litres of water. Leave it for half an hour, then empty the tank and flush it through. Repeat the process, maybe several times if your tank is really contaminated. Then refill with fresh water to which you add bleach at the rate of 1ml per 100 litres; this concentration should kill any remaining bugs but is safe to drink.

 

[kandoma]

the stuff used for dishwashers is safe to use and very strong. But very important: you have first to dissolve the cristals in hot water, then wash your tank.

Peter

 

[HeadMistress]

The recommended method

The following recommendations conform to section 10.8 in the A-1 192 code covering electrical, plumbing, and heating of recreational vehicles. The solution is approved and recommended by competent health officials. It may be used in a new system a used one that has not been used for a period of time, or one that may have been contaminated.

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 1/2 cup (4 oz or 100 ml) Clorox or Purex household bleach (5% sodium Hypochlorite solution.) Be sure to use bleach that does not contain any additives.

With tank empty, pour chlorine solution into tank. Use one gallon of solution for each 5 gallons of tank capacity. (There's an easier way to to do this: measure the right amount: use 100 ml bleach per 10 gallon water tank capacity...for larger tanks a quart or liter to 50 gallons... mix in any dilute that suits you before putting in the tank.)

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.

People have expressed concern about using this method to recommission aluminum tanks. While bleach (chlorine) IS corrosive, it’s effects are are cumulative. So the effect of an annual or semi-annual "shock treatment" that's flushed completely out within 24 hours 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.

 

[jimbouy]

Re: The recommended method

Hi Peggy.


This info is usefull to me as my tank hasn't been used for many years.

Can you clarify what sort of bleach we should be using.

I know your US based so brand names might be a problem.

Would I be right in thinking ...not the super thick clingy stuff or the pink nice smelly ones?

Jimbouy

 

[pvb]

Brands...

I think you're right that Peggy, being based in the US, might not be too familiar with our brands. You're also right to assume you shouldn't use the "modified" bleaches on the market. I've always used the very cheapest own-brand supermarket bleach for this purpose - the stuff that literally costs pennies a bottle. I reckon that if it's really cheap, the supermarkets couldn't have afforded to put any significant additives in it.

 

[ashanta]

Do you have an inspection lid on the tank? I have a GRP tank that does not have a drain tap. It only has the outlet to the pump and sink. but I have two round screw top lids which means I can wash the tank fully with detergent and bleach, rinse and refill with clean water. I do not use purifying tabs as they alter the taste of the water. I use an inline filter under the sink. I do this each season and it works well. If you do not have an inspection lid you could always fit one if you have access to the top part of the tank.

Regards.

Peter

 

[jimbouy]

Re: Brands...

So corner shop stuff then.

The white vinegar tip is one I would never have thought of either.

I wish I had electrically pumped water...... my foot is going to ache. May be I'll have to rig up some sort of syphon.

Regards to all.

Jimbouy

 

[Gunfleet]

Re: The recommended method

Adding a carbon filter in the line from the tank gets rid of any lingering taste from your cleaning method. My boat has a 38 year old galvanised cistern fitted just above the deep keel. It's cold, dark and the water comes out of it absolutely beautiful!

 

[Thistle]

Re: Brands...

Can you get at the piping on the tank side of the footpump so that you could put in a temporary electric pump, for example on an electric drill?

 

[pvb]

Or how about...

When I'm emptying my water tank for cleaning/flushing, I just remove the outlet pipe and let it all fall into the bilge, then use the bilge pump to get rid of it.

 

[jimbouy]

Re: Or how about...

Unfortunately Centaur bilges are unhelpfull in that respect as they don't easily flow from one end to the other. So this can involve hand pumping forward sections.

But when she settles on the mud I reckon I can stuff a hose down thru the filler and syphon most of the water.

 

[VicS]

Re: Domestic bleaches

I agree with pvb that one should avoid bleaches with additives, they are for laundery use and cleaning drains, and use one which is only sodium hypochlorite but whether the cheaper supermarket own brands fall into that category I would not like to say without reading the label.

Some while back one of the forum members also pointed out that there was a risk that less pure hypochlorite may also contain chlorate (as in weed killer).

For the these reasons I would recommend the use of Milton rather than household bleach. If it's suitable for sterilising babies bottles then it's not going to cause us any harm if used in our water tanks. I know its much more expensive than bleach but, come on, you are only buying 250 cc not a few thousand litres, it's not going to make a significant dent in the boating budget is it.

One day the makers of Milton are going to read the statemnt that it is "only expensive, watered down bleach" and send the Lawyers in. That'll put a dent in your boating budget.

 

[HeadMistress]

Re: The recommended method

Jimbuoy, Everyone who answered your question before I got here is right...use only bleach that's just plain liquid bleach...5% or better. Avoid all others.

Just cleaning the tank is only half the job. Although most people think only in terms of the tank, the plumbing is actually the source of most foul water, because the molds, mildew, fungi and bacteria which cause it thrive in damp dark places, not under water. So it's very important to make sure the solution gets into the lines and the system is kept pressurized to keep it in the lines during the recommissioning process (I realize this may not be easy if you don't have an electric water pump...do the best you can).

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 should be in addition to, 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--wash the boat 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.

And finally, none of this is intended to be water purification advice...but only to recover a system that may have become contaminated and/or general maintenance for systems taking on municipal water that's already been purified. Consult a water purification specialist when cruising to areas where water may be suspect...and when in doubt, boil all water before using it until you can recommission the system acccording the previous instructions.

 

[VicS]

Re: Dock hoses

Better to avoid the "dock" hose as you call it. It's not unknown for some idiots to stick it all the way into the toilet holding tank to flush that out. YUK Far better to use you own hose. For perhaps this reason but also the reasons you indicate I believe in places "dock" hoses have been removed.

 

[HeadMistress]

Re: Dock hoses

The dock supply line is the line from the water main to the faucet on the dock...typically a pipe or hose attached to the underside of the dock, so it's exposed to summer warmth all day, every day...flushed out only when someone uses water. So unless you come right behind someone who's used plenty of water, let it run. It's fairly easy to tell when it's been flushed out...the water that's been sitting in it will be warm...becoming cold when "new" water comes through.

Marinas here in the U.S. provide water faucets on the docks for each of their slip holders. Only trailered boats and those kept on moorings have to use public docks to fill their tanks. We keep our own hoses connected to 'em, coiled up when not in use...which means that not only the dock supply line, but our own hoses too, get very warm...and most aren't used except on weekends. So our own hoses provide the ideal environment for growing those "critters" that create foul--albeit safe (unless you're dumb enough to use the same hose to flush out a waste tank)--water aboard.

So let the water run till it turns cold no matter where you fill your tanks.