Sanitising water tank protocol

[CarpeDiem 355]

What do people do to sanitise their water tanks? 

Our tanks (2x200l) are built in part of the furniture structure. They are fibreglass, either polyester or epoxy and I was told they were oven cured. 

I put one of those USB endoscopy cameras into the tank a few years ago and it wasn't clean by any stretch of the imagination.  It is full of baffles, so cutting it open and adding an inspection port for cleaning isn't a option.

Our water was gross when we got the boat. So this is what we do now. 

Each year, about now. I remove the filters and fill the tanks and plumbing with 50ppm bleach and take it for a sail.

24hrs later, if the free chlorine is under 10ppm empty and repeat the above.  (only happened the first time we did it) 

Then I give it three flushes with marina water and make sure the free cl is down to drinking levels.  Install new filters and we're done for another year...

I put the old filter back on when flushing the concentrate, cause I wouldn't want to kill the fanworm in Westhaven.

Now that we have never had any problems with foul water, I am wondering if this is overkill and what others do for their tanks? 

 

 

 

 

[aardvarkash10 866]

2 X 50 litre flex tanks.  A cap of unscented janola every complete fill.  Water is roof collected, not town supply.

[ex Elly 161]

I used to do chlorine solution for 24 hours, followed by white vinegar solution for 24 hours. Saves doing the 3 flushes.

 

[Ex Machina 338]

Slight drift but we treat our home tanks with this stuff and I would use it on a boat tank if I had one . I don’t like bleach and I don’t like waterborne gut bugs . Our water doesn’t smell because it’s rain water so it only goes through a .5 micron paper filter for bugs ….if I had a fusty boat tank a charcoal filter would sort out any flavours including chlorine/garden hose vinyl flavours from marina  supply .

 

https://www.mitre10.co.nz/shop/pour-n-go-water-tank-treatment-2-litre-clear/p/109787

[LBD 76]

What Aadvark says... I used to look after many tourist vessels and this became std practice to comply with " Clean water standards" we used Miltons.

 

 

[grant 39]

for those with filters, do you filter the water going into the tanks or when it comes out? and what filters do you use?

thanks

 

[CarpeDiem 355]

2 hours ago, grant said:

for those with filters, do you filter the water going into the tanks or when it comes out? and what filters do you use?

thanks

 

On the boat side.

I have a strainer before the pump, a Jabsco filter after the pump, and a 0.5 micron filter on a dedicated drinking water tap.

The replacement jabsco filter is now rediculously expensive, it was $54 last year, so I will probably replace it with something more cost effective as I can get a housing and a filter for less than a replacement jabsco filter. 

I don't see any value in a fixed installation shore side filter.  Maybe if I had a water maker and needed to keep chlorine out of the system.  I know lots of boats and RVs have them. 

[southernman 73]

Installation of a carbon filter on the outlet will remove most of the taste and odour issues with chlorinated water.  It's good to fill the tank with treated water and hold a residual then remove it at point of use.  

0.5 micron is good but if you want to make sure that nothing gets past make sure you use a absolute cartridge rather than a nominal one and increase it to 1 micron if you like.  

Aftermarket standard 10" housings are the cheapest to run rather than smaller 5" ones which are hard to source and expensive.  Only issue is that they take more room up!  

If you want to replace chlorine, you can use chlorine dioxide which has less taste and odour.  

[grant 39]

22 hours ago, CarpeDiem said:

On the boat side.

I have a strainer before the pump, a Jabsco filter after the pump, and a 0.5 micron filter on a dedicated drinking water tap.

The replacement jabsco filter is now rediculously expensive, it was $54 last year, so I will probably replace it with something more cost effective as I can get a housing and a filter for less than a replacement jabsco filter. 

I don't see any value in a fixed installation shore side filter.  Maybe if I had a water maker and needed to keep chlorine out of the system.  I know lots of boats and RVs have them. 

thanks for that and the links,

one question, why do you have the Jabsco and the 0.5 micron filter? From what I can see it looks like they both do much the same thing?

[1paulg 16]

chlorine destroys carbon filters pretty quickly - I wouldnt recommend using anything v low concentrations otherwise factor in writing off your carbon filters as part of that process and replace 

[Island Time 1,174]

1 hour ago, 1paulg said:

chlorine destroys carbon filters pretty quickly - I wouldnt recommend using anything v low concentrations otherwise factor in writing off your carbon filters as part of that process and replace 

Source please? My understanding it that Activated carbon filters are used to remove chlorine? Certainly we have shock dosed our watertanks and not had issues with the drinking water via the 0.5 micron carbon filter. Water tasted fine ... 

[CarpeDiem 355]

2 hours ago, Island Time said:

Source please? My understanding it that Activated carbon filters are used to remove chlorine? Certainly we have shock dosed our watertanks and not had issues with the drinking water via the 0.5 micron carbon filter. Water tasted fine ... 

Carbon filters "remove chlorine" via a chemical reaction.  Free chlorine in water is HOCl and OCl-.  Which is pretty much where my knowledge ends.... 

So taking a guess, the carbon gets oxidised into CO, CO2 or COO-.

And we have a chloride and hydrogen ion left over... I have no idea what happens to the chloride ion (Cl-)... It's a salt, so I guess we drink it? And I suppose the H+ joins the rest of the hydrogen in the atmosphere.... Or we drink that too and fart it out. 

The more the carbon oxidises the more blocked the filter will become, I sppose a lot of that would end up back in water and we drink that too (or it escapes to the atmosphere). 

So it stands to reason that the more chlorine that the filter 'removes' the quicker it will run out of Carbon surface area.... But I don't know how much you'd need to have an effect.

Most filters are rated for 30000+ litres. I would assume that these are calculated based on 4ppm free chlorine which is the upper maximum for drinking water.  Auckland water is closer to 0.5ppm...

I think shocking the system to say 200ppm and running that through the filter would probably use up the carbon quite quickly. But I do not know how quick. 

 

 

 

[CarpeDiem 355]

2 hours ago, grant said:

thanks for that and the links,

one question, why do you have the Jabsco and the 0.5 micron filter? From what I can see it looks like they both do much the same thing?

The 0.5 micron filter results in a slower velocity. Which means more contact with the carbon which means less Chlorine. 

Jabsco don't publish the filtration size of their filter, but an educated guess puts it at 10microns. So the 0.5 also catches any smaller nasties that the Jabsco misses. 

The 0.5u is also too slow for general use.

[CarpeDiem 355]

On 11/12/2022 at 12:06 PM, Ex Machina said:

Slight drift but we treat our home tanks with this stuff and I would use it on a boat tank if I had one . I don’t like bleach and I don’t like waterborne gut bugs . Our water doesn’t smell because it’s rain water so it only goes through a .5 micron paper filter for bugs ….if I had a fusty boat tank a charcoal filter would sort out any flavours including chlorine/garden hose vinyl flavours from marina  supply .

 

https://www.mitre10.co.nz/shop/pour-n-go-water-tank-treatment-2-litre-clear/p/109787

That's Hydrogen Peroxide. I have often thought about using that but have never been able to find any good sources for what concentration to use. 

Interestingly that product is 7.5% while food grade h2o2 is 33%. It's also stabilised with silver so it will hang out in the water indefinitely until it runs into something biological. 

It's amazing the crap we drink... Water is anything but H2O

I will look at this. Thanks. 

[MartinRF 38]

9 hours ago, CarpeDiem said:

That's Hydrogen Peroxide. I have often thought about using that but have never been able to find any good sources for what concentration to use.

That was what we used in our fresh water tank when I did my military service in the Swedish navy 40 years ago. I don't remember the dosage but we always added some when filling water tanks.

Hydrogen peroxide was also part of the fuel for some torpedo models but that is another story.

/Martin

[Black Panther 1,496]

I don't do anything.  Never had a problem. 

[Ex Machina 338]

54 minutes ago, Black Panther said:

I don't do anything.  Never had a problem. 

I never had a problem until I got giardia . Don’t ever want to get a waterborne illness again 

[Vivaldi 47]

7 hours ago, Black Panther said:

I don't do anything.  Never had a problem. 

Same - fill tanks, drink it, fill tanks again. Always keep them full between trips. 

[Terry B 63]

I always used the chlorine 'pills' you can get from the likes of Burnsco and camper van places. Yes, marina water is chlorinated but my tanks aren't.

Pop a cuppa pills in (after reading instructions) and away you go. Not every fill, but frequently. Never noticed a taste change - but 30 years of smoking may be the cause

Plus every year or so (whenever I remember) a bit of bleach with serious flush through.

No filters (have never had filters at home and never had a problem so can't see why it would be necessary on a boat that only travels in NZ where chlorinated water is very common). Or am I wrong here?

[1paulg 16]

On 12/12/2022 at 9:19 PM, Island Time said:

Source please? My understanding it that Activated carbon filters are used to remove chlorine? Certainly we have shock dosed our watertanks and not had issues with the drinking water via the 0.5 micron carbon filter. Water tasted fine ... 

My understanding is that a carbon filter will take out the chlorine in a shock dose but it will most likely end up needing to be replaced afterwards - small amounts are ok but not shock doses ....Tryiing to remember who told me that -was some marine outlet but can check on this....