Water filtration

sarabande

sarabande

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I missed SIBS, so apologies for this. ( I have done my homework on previous 2006 threads ! )

We have a close sailing friend who has developed a pretty heavily-compromised immune system, and we want to ensure that our on-board drinking water is as clean from impurities and bugs, as possible, so that she (and we) do not have to worry about bringing bottled water on board, which is our present, clumsy and expensive, practice.

Apart from filling the water tank, bunging in some evil (cheap !) agricultural sterilising chemicals, and then emptying it, what advice can Forum members give in response to the following issues, please ?

<u>Supply side into tank</u>
We are buying our own water hose, but what sort of filter can be used at the delivery end to ensure that particulate, or oocyst contamination is removed ? Are there any filters which we can use at the same time to remove bacteria ? These filters must work at a relatively low water pressure from the/any marina's pontoon tap; if this is not practical we have to filter on board, so....

<u>Delivery side from tank</u>
This is probably at a higher pressure than shore supply, so what
filters would you advise to ensure that we can produce cold and hot "cleaned" water ?

<u>System</u>
There's a 150 gallon fresh water tank, to a pressure pump which delivers both to the coldwater system and to the immersion heating tank, thence to a galley sink, a handbasin in the heads, and a shower.

This may sound to be rather OTT, but we are prepared to do as much as we can to avoid the risks of any water-derived illness for our frequent, and loved crew member.

I would be grateful for any practical advice on design and set up of a system, and for recommendations of suppliers / manufacturers of readily available filters or cartridges. I propose to do the work myself (i.e. help the family's Chief Technical Operations Manager to do it !) so bonded suppliers who only supply and fit are out.

In anticipation, many thanks. S
 
If you want to remove organisms, you need to filter to less than one micron. This removes all living matter (at least, all the stuff that concerns us in the treatment of food and drink). You have a choice of filtering all water coming on board or just the drinking water - if your friend is likely to accidentally drink the raw tank water when bathing or brushing teeth, then maybe you need to consider this.

For filtering all incoming water you will need a filter housing. I used Derwent water in June for cartridges and found them reliable and easy to do business with. See Derwent water housings Now you need the filter elements. The ones you are looking for are here and the write-up tells you about what they filter out Filter cartridges

If you only want to filter the drinking supply I recommend the General Ecology filters which we have been using for two years. They are brilliant, and give taste-free and totally safe water from grotty tank water. See General Ecology filters

Good luck.
 
I agree with the general ecology filters, thats the one I have and has been excellent, would reccomend them. But only use it for drinking/cooking, as the whole system would need filters replacing very often and they are expensive. Much cheaper than bottled water and probaly better.
 
You're welcome /forums/images/graemlins/smile.gif You need to order the O rings as a separate item. It is also worth replacing the flex hose from the filter to the faucet every so often, especially in hard water. Here in Spain the DIY shops keep a range of those so no prob but you might need to order one from GE if in the UK?
 
suggest that in addition to a decent filter between tank and tap which will filter out a large percentage of the impurities, you also invest in a UV treatment to deal with any bacteria. Some people have a small drinking water tank so that they only have to maintain a small tank and reduced water throughput.
 
The cheapest solution would be:

First - if your tank is not clean so that it taints the water, then clean it.

Second - tell your friend that you have installed some super filtration/disinfecting filter. If they are of the nosey type, put an empty cheap filter body (or something that looks like one) in line for them to look at.

John
 
I suspect that if one was that compromised one would not be mixing with other peeps, all food sterilised, only bottled sterilised water, etc, etc.

But I am open to being convinced /forums/images/graemlins/smile.gif.

John
 
Please be very wary of filtering into the tank. A lot of the filters remove chlorine and thus the self-sterilisation of the water is eliminated thus allowing things to grow in the tanks.

If you really must have the waters filtered then put your filters as near as possible to the taps and ensure that each time you go onboard you firat of all flush out at least twice as much as the dead volume of filtered water that has sat unsterilised since you last used the boat.

To do as you suggest means at least two stage filtration as a 1 micron filter will clog up pretty quickly unless pre-filtered by 5 or 10 micron filters.

To clean up the whole water supply buy the sterilisation tablets and sterilise the whole system an flush before fitting the filters
 
I don't agree with you. The free chlorine does not last very long, in practice though in any case most of the filters that anyone would use for pre-filtering a whole tank would not include carbon. The ones I directed sarablonde to do not have activated charcoal so do not remove chlorine.

As for filters, I use five micron filters for my watermaker - I use the spun polyester type with depth filtration rather than the surface plaited type but whichever type you find that the larger particles just clump on the surface without blocking the finer pores. I don't know why, but I noticed this myself and remarked to the watermaker manufacturer who said that is is a well known fact. That's why they don't fit a pre-filter below 5 micron despite there being all manner of things larger than that. I do have a very coarse pre-filter, of about 0.5mm but that's to keep insects and bits of grot out. For tap water, I don't see the need to pre-filter before a 1 micron filter and if there is a problem it would be very easy to fit another filter upstream, if needed.

I'm not sure about using sterilisation tablets in this case. We don't have the details but many people who have compromised immune systems are going through a course of radio/chemo therapy and I would think it's wisest to keep chemicals to the lowest level practicable.

Of course this does beg the question whether they would be better off with bottled water. Having read the General Ecology data sheet I have more confidence in our filtered tap water on board than I have in any bottled water on the market. I just don't trust suppliers. Sad and cynical, I suppose, but not without good cause when it comes to things like firms making more profit with hardly any risk of malpractice being detected.
 
It was on our first outing that I made the mistake of pouring SWMBO a glass of water just after filling up the tank and adding a generous number of Puritabs. She was not impressed!

We use a Kenwood filter jug at home, so I bought a second, smaller one and that tastes fine. I suppose I could cheat with a placebo, but I quite like the taste so the filters are real and changed regularly.

Is that a technical or moral solution???
 
Thanks all for your varied contributions and expertise. Off to set up:

1 a coarse filter at the end of the hose on input to the tank
2 a medium filter on the output from the tank to all the water system
3 a fine, carbon-based "health/ecological" filter below the galley tap, marked "Filtered"

I hope this gives my friend (a kidney patient for whom even a few bugs can mean a stay in hospital) a chance to keep on sailing, and us up to date with the latest scandals in the world of Hire Edikashun.

most grateful. S


/forums/images/graemlins/grin.gif
 
Unless you are going to make the incoming tap water safe (which presumably you are not) then 5 microns will usually filter out rust from the incoming supply if that is an issue? Otherwise I don't see what a 'coarse' filter will do for you there. It is sensible to put a filter on the tank outlet as this stops crud from getting into your pump - usually this is quite coarse, a stainless gauze. You might already have one there?

The galley faucet is the most important thing. When you say 'carbon based' please remember that fine filtration (0.1 micron) is important for the bugs and cysts while carbon is for taste and certain chemical pollutants. You really need a combination, not simply a carbon-based or you will not filter out the pathogens.

The one that came out best in all the recent (?)PBO tests was the General Ecology. They reckon you can drink Ganges water after it has been filtered in a General Ecology filter but I don't think I'll try!
 
Point taken. The great water plan has been modified to include your advice to include the very fine particulate filter as well as the "eco" filter at the galley.

very many thanks

S.
 
That's only IF you feel that you need it. We are perfectly comfortable with just the General Ecology filter but then we don't have medical issues. However, by putting in the extra filter you do remove potential food for pathogens making your tank less likely to be a breeding ground for bugs. 5 microns would be a good size for that without too much of a pressure drop and it will in practice filter out most of the pathogens as they tend to be on bits of stuff rather than floating around alone, I believe. Good luck with it. By the way, consider buying the filters in bulk - we buy a few dozens at a time as it is much cheaper. 5 micron 97/8" is a common standard for water makers so you might be able to share a box with others in your club or area.
 
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