Fitting water maker using heads intake pipe!

[geem]

I guess most people would not choose to use sea water in 'a busy anchorage'? There are many cautions about using water makers in those same anchorages, perhaps more biocide use is called for in those conditions?

Watermakers are safe to use in dirty water. Even where toilets are discharged. Oily water will damage the HP membrane so we are careful where we use the watermaker. The UV filter adds an extra layer of protection to our water before it enters the water tank. UV filtration and RO watermaking go well together. UV doesnt work well unless the water is super clean. Bacteria can hide behind particles in water and not get the UV zap due to shadow effect.
The only problem running the watermaker in dirty water is sediment contaminating the watermaker prefilters quickly. Its more important to keep prefilters clean on 12v watermakers than on 220v units like mine. We have a powerful 220v feed pump that can take a lot of pressure build up from dirty filters. This isn't the case on 12v feed pumps. They soon struggle with any pressure build up and then you starve the HP pump. This isn't good for the 12v HP pumps.
You should be able to make water in a busy anchorage since this is where you spend a lot of time. If you are going for a 12v watermaker the run time will be measured in hours per day. Where else are you going to make water? We average 15-20mins use per day but choose normally to run the watermaker every other day for about 30-40 mins. Once you get to three days of none use you risk bacterial contamination of the system simply due to dying plankton in the pre filters and pipework. The system gets smelly and your TDS readings increase. This is less of a problem in cool water.
Good luck with your installation ?

 

[pyrojames]

If you feel the need for a wayermaker you will also need seawater in the galley, in order to conserve the expensive H20. Use a common intake for both.

I always felt that the water is my tanks was more valuable when I didn't have a watermaker! After I fitted a watermaker, we started washing everything in fresh water instead.

 

[geem]

I always felt that the water is my tanks was more valuable when I didn't have a watermaker! After I fitted a watermaker, we started washing everything in fresh water instead.

Exactly. My experience on our previous boat that had a 12v watermaker and saltwater pump in the galley was that we only used the saltwater pump when crossing the Atlantic. We didnt like using it at anchor as the water isnt clean. We hardly used it so removed it.

 

[Moodysailor]

Watermakers are safe to use in dirty water. Even where toilets are discharged. Oily water will damage the HP membrane so we are careful where we use the watermaker. The UV filter adds an extra layer of protection to our water before it enters the water tank. UV filtration and RO watermaking go well together. UV doesnt work well unless the water is super clean. Bacteria can hide behind particles in water and not get the UV zap due to shadow effect.
The only problem running the watermaker in dirty water is sediment contaminating the watermaker prefilters quickly. Its more important to keep prefilters clean on 12v watermakers than on 220v units like mine. We have a powerful 220v feed pump that can take a lot of pressure build up from dirty filters. This isn't the case on 12v feed pumps. They soon struggle with any pressure build up and then you starve the HP pump. This isn't good for the 12v HP pumps.
You should be able to make water in a busy anchorage since this is where you spend a lot of time. If you are going for a 12v watermaker the run time will be measured in hours per day. Where else are you going to make water? We average 15-20mins use per day but choose normally to run the watermaker every other day for about 30-40 mins. Once you get to three days of none use you risk bacterial contamination of the system simply due to dying plankton in the pre filters and pipework. The system gets smelly and your TDS readings increase. This is less of a problem in cool water.
Good luck with your installation ?

I think it is worth clarifying this statement a bit further, around the definition of dirty water.

There is a difference between water that is dirty due to suspended particles (dirt, weed, growth, etc) and water that is dirty due to bacterial contamination. You could have water that appears dirty to look at, but has low bacterial content, or water that appears clean but has high bacterial content. I work in the field of ballast water treatment on large commercial ships and the principles are very similar on the first stage. In a former life I also installed a number of watermakers on powerboats whilst working in Florida.

As well stated here, the filters will do the job of removing organic mater and sediment, but the cleaner you can keep the incoming water, the more effective this will be, and subsequently the longer you can go between filter maintenance intervals.

Unless you have a test kit you won't be able to tell the bacterial content of the water, so I would encourage a combination of good management and disinfection here either by water treatment or UV sterilization. Good management would just simply be being aware of your environment and either not making water where you feel the source water could be heavily contaminated, or mitigating (treatment or separate tanks and testing).

Also, as well mentioned, RO watermakers don't like oil at all, so unless you have a very good oil pre-filtration systems, pay very close attention to oil contamination.

Good luck to the OP (and anyone else) with the install.

 

[geem]

I think it is worth clarifying this statement a bit further, around the definition of dirty water.

There is a difference between water that is dirty due to suspended particles (dirt, weed, growth, etc) and water that is dirty due to bacterial contamination. You could have water that appears dirty to look at, but has low bacterial content, or water that appears clean but has high bacterial content. I work in the field of ballast water treatment on large commercial ships and the principles are very similar on the first stage. In a former life I also installed a number of watermakers on powerboats whilst working in Florida.

As well stated here, the filters will do the job of removing organic mater and sediment, but the cleaner you can keep the incoming water, the more effective this will be, and subsequently the longer you can go between filter maintenance intervals.

Unless you have a test kit you won't be able to tell the bacterial content of the water, so I would encourage a combination of good management and disinfection here either by water treatment or UV sterilization. Good management would just simply be being aware of your environment and either not making water where you feel the source water could be heavily contaminated, or mitigating (treatment or separate tanks and testing).

Also, as well mentioned, RO watermakers don't like oil at all, so unless you have a very good oil pre-filtration systems, pay very close attention to oil contamination.

Good luck to the OP (and anyone else) with the install.

I dont disagree but there will be times when you need to make water when the inlet water is contaminated with sediment or bacteria of both. I was trying to clarify that making water in this situation isn't a problem as long as you keep an eye on your prefilters and ideally use UV treatment. We will make a tank full of RO water if we know we are going to be going to a dirty anchorage for a couple of weeks. A 200gallon tank helps. Otherwise we rarely fill the tank more than half full. An example would be the lagoon at St Marten. Its full of yachts and a few fuel docks. The risk of oily water is high here so we dont use the watermaker.
With regard to prefilters, we tend to hang the dirty 20 micron prefilter over the side of the boat on a string for 24hrs to knock the lumps out. It gets the filter quite clean. We simple swap it for a clean one whist the filter is dangling. We then dry the filter in the sun( a bit of UV) then its ready to be installed next time. If we do this then the 5 micron prefilter stays pretty clean for months on end. Its also worth having your 10” prefilters mounted in clear housings. You can see at a glance if filters are going dirty. We don't bother with pressure gauges on our filters since the 220v feed pump can develop so much pressure and if the filter goes dirt we simply change it

 

[Moodysailor]

I dont disagree but there will be times when you need to make water when the inlet water is contaminated with sediment or bacteria of both. I was trying to clarify that making water in this situation isn't a problem as long as you keep an eye on your prefilters and ideally use UV treatment. We will make a tank full of RO water if we know we are going to be going to a dirty anchorage for a couple of weeks. A 200gallon tank helps. Otherwise we rarely fill the tank more than half full. An example would be the lagoon at St Marten. Its full of yachts and a few fuel docks. The risk of oily water is high here so we dont use the watermaker.
With regard to prefilters, we tend to hang the dirty 20 micron prefilter over the side of the boat on a string for 24hrs to knock the lumps out. It gets the filter quite clean. We simple swap it for a clean one whist the filter is dangling. We then dry the filter in the sun( a bit of UV) then its ready to be installed next time. If we do this then the 5 micron prefilter stays pretty clean for months on end. Its also worth having your 10” prefilters mounted in clear housings. You can see at a glance if filters are going dirty. We don't bother with pressure gauges on our filters since the 220v feed pump can develop so much pressure and if the filter goes dirt we simply change it

Good advice from the practical reality of living & using one.

 

[richardh10]

Hi geem
As a matter of interest, what type of uv filter do you use, and where in the system is it fitted?
Thanks

 

[geem]

Hi geem
As a matter of interest, what type of uv filter do you use, and where in the system is it fitted?
Thanks

Mine is designed for use on an aquarium. It cost about £50. You need to match the size of the unit to the flow rate. There is a dwell time requirement for the UV light to be effective. Mine is an AC unit which works fine for us as the watermaker is powered by the diesel genset. You can by 12v UV filters but they are more expensive.
Mine is installed as the last item on the watermaker system so it zaps the water before it enters the tank. We did a full tank clean a couple of years ago when we took the two big access lids off and climbed in with a scrubbing brush. Once we had finished we sterilised the tank. Since then its only been filled with RO water. Hope this helps

 

[dgadee]

Once we had finished we sterilised the tank. Since then its only been filled with RO water. Hope this helps

I took the view that leaving only RO water in the tank for longish periods wasn't so good. I am happy to mix treated and RO water - it all passes through a carbon filter before being used to clean out the pressure vessels. Does the UV mean that there will not be any chance of anything developing in your tank over the winter, say?

 

[geem]

I took the view that leaving only RO water in the tank for longish periods wasn't so good. I am happy to mix treated and RO water - it all passes through a carbon filter before being used to clean out the pressure vessels. Does the UV mean that there will not be any chance of anything developing in your tank over the winter, say?

My view is that RO water thats been UV treated is a safer bet than water that come from a tap somewhere. Having said that, we normally cruise in the Caribbean where water quality alongside is of dubious quality. In the UK we would likely not use the watermaker.

 

[Spirit (of Glenans)]

Thanks @Neeves and @Moodysailor - on reflection I doubt that opposite the heads would indeed be far enough away for watermaker (and it’s just forward of the keel too), but it would still work well for a deckwash and also galley feed.

I guess you can always ‘decommission’ the heads while desal is running? I did think this with the OP’s predicament: a simple option could be just to divert/shut off the heads inlet with a ‘changeover’ valve for the watermaker. Presumably one can do without flushing for a time, to guarantee no blackwater gets to the watermaker?

Would be very do-able if there was a holding tank installed.

 

[geem]

Would be very do-able if there was a holding tank installed.

Since we only run our watermaker for 30-40 mins at a time not using the heads for that period is no hardship. Our intake is towards the back of the boat so a reasonable distance from the forward heads. We still choose not to use the heads. If you are running a low output 12v watermaker then using the holding tank during the several hours that these units normally need to run for makes a lot of sense

 

[dankilb]

Thanks - the location (opposite heads) would be the best, and maybe only, logical location anyway. On a 42' AWB there just isn't much available space. And it's immediately adjacent to the 'best' (stainless not GRP) water tank under the forepeak. We have a second - composting - heads which, for all its sins, provides a backup (no holding tank).

 

[pcatterall]

Mine is designed for use on an aquarium. It cost about £50. You need to match the size of the unit to the flow rate. There is a dwell time requirement for the UV light to be effective. Mine is an AC unit which works fine for us as the watermaker is powered by the diesel genset. You can by 12v UV filters but they are more expensive.
Mine is installed as the last item on the watermaker system so it zaps the water before it enters the tank. We did a full tank clean a couple of years ago when we took the two big access lids off and climbed in with a scrubbing brush. Once we had finished we sterilised the tank. Since then its only been filled with RO water. Hope this helps

Have these UV filters any part to play in cleaning 'dodgy' town water? Our 'town water' in Spain is regarded as not suitable to drink, I do wonder if this is really the case as so many people now regard anything not in a bottle and passed through a volcano as suspect ( corporation pop suits me here on the Pennines!) Our 100 gallon tank will last a good while with our 3 man crew, if we are relying on it we treat the whole tank load with aqua sol and then our ( carbon granule?) filter helps remove the aqua sol taste. Would a uv filter help here.

 

[geem]

Have these UV filters any part to play in cleaning 'dodgy' town water? Our 'town water' in Spain is regarded as not suitable to drink, I do wonder if this is really the case as so many people now regard anything not in a bottle and passed through a volcano as suspect ( corporation pop suits me here on the Pennines!) Our 100 gallon tank will last a good while with our 3 man crew, if we are relying on it we treat the whole tank load with aqua sol and then our ( carbon granule?) filter helps remove the aqua sol taste. Would a uv filter help here.

Yes, we had a spring water supply at our last house. It was our only so water supply. It was not a great supply. It got run off in to the spring in very heavy rain.
On your house I would suggest that you install a 5 micron filter followed by a one micron filter in clear 10” housings prior to a UV filter. This will ensure you remove as much particulate as possible prior to the UV filter. This is what we did at our house and it worked well.
On your boat I am not sure how you could use the UV filter. I believe there are UV filters that can go on the discharge side of the tank that will run on 12v that will switch on with the pump but they are expensive.