Water filtration and reverse osmosis. Advice wanted.

[Jomac]

I'm considering buying a 32 foot boat to convert into a live aboard. Most area's i have covered but there is just one that i'm confused and thats getting reasonably clean water to use on board.

The boat could be moored in salt water or fresh water and a sliding scale between the two. I've been looking at reverse osmosis for getting drinkable water from a fresh water source, and for sea water, the topic moves onto desalination plants. Other sources say that some RO systems can filter out the sodium. Then we have 2 stage up to 6 stage RO systems and matters get confusing.

All i am looking for is a simple, easy to maintain system that wont cost an arm and a leg to maintain .I would be looking at no more than a couple of gallons a day, the water would be for shower and washing up. I may make the odd cup of tea but i doubt I would be drinking straight from the tap.

Is there an easy to follow guide to answer my questions and fill in the gaps? If possible, I would prefer to build my own system to save money.

TIA

 

[billskip]

Water maker

This link from cherod thread in pbo

 

[Jomac]

This link from cherod thread in pbo

I had a search for pbo and Cherod and didnt find anything, do you have a link?

 

[chrishscorp]

Using RO for washing up and a shower should be ok but is not ok for drinking or cooking with

 

[billskip]

I had a search for pbo and Cherod and didnt find anything, do you have a link?

Click on Water maker in my post...that is a link...?

 

[Yngmar]

The cheap freshwater RO systems you can buy at the plumbing suppliers for houses should work in freshwater lakes (with some prefiltering), but will not work at all with seawater, as they can't generate the required pressure. For desalinating saltwater you will need a proper marine watermaker, which will cost you from around €1k for a self built one or €3-5k for a basic kit one. They don't cost an arm and a leg to maintain, only to purchase!

 

[mikegunn]

Using RO for washing up and a shower should be ok but is not ok for drinking or cooking with

Why is it not OK for drinking and cooking? I’ve used a RO watermaker for 13 years with apparently no ill effect. I would agree that it is devoid of any mineral content, but that can always be added, to taste.
Mike

 

[chrishscorp]

Why is it not OK for drinking and cooking? I’ve used a RO watermaker for 13 years with apparently no ill effect. I would agree that it is devoid of any mineral content, but that can always be added, to taste.
Mike

You need to re mineralise the water, its not just for taste.

Two of the minerals that are stripped out that are key are calcium and magnesium, RO will seek to remineralise itself and the easiest way for it to do that is for it to leach these minerals out of your body usually the bone structure. There are other health issues it can cause, some serious.

Some light bedtime reading for you from the World Health Organisation
https://www.who.int/water_sanitation_health/dwq/nutrientschap12.pdf

 

[halcyon]

Is this a future option ?

Brian

 

[Outinthedinghy]

My boat was built with filtration in mind although never fully fitted.

What was fitted however is a 4ftx1ftx18 inches steel settling tank. This takes water in (I'm on the Thames) and you detain the water for 24h to allow the silt to descend to the bottom of the tank.

Fitting for onward transfer to filters and a fitting for silt removal with a diaphragm pump.

Works quite well. I then pump it through a manifold of 3 filters 50 micron, 20 micron and 5 micron then a UV lamp then add chlorine tablets to final water product. That is for washing and flushing. It's been ok.

A small domestic RO system then takes water from that supply and can if needed produce a few gallons a day of clean (TDS around 20) water. This needs to be remineralised ideally.

The boat has 5 separate water tanks so two are for the settled/filtered river water and the other three which are below the solid fuel stove to avoid freezing can be used to store a large volume of clean water either from landside taps or RO water remineralised.

Don't know about salt water but I think that gets expensive although if it's only a small amount perhaps one of those manual ones would be ok.

 

[mikegunn]

You need to re mineralise the water, its not just for taste.

Two of the minerals that are stripped out that are key are calcium and magnesium, RO will seek to remineralise itself and the easiest way for it to do that is for it to leach these minerals out of your body usually the bone structure. There are other health issues it can cause, some serious.

Some light bedtime reading for you from the World Health Organisation
https://www.who.int/water_sanitation_health/dwq/nutrientschap12.pdf

Thank you for the link to the report, of which I was aware. I do feel however that the report contains too many “may” and “could” to be truly conclusive. However, I must apologise if I came over as glib in saying “to taste”. That was not my intent. In recognising that RO water is devoid of minerals it is my opinion that the matter can be addressed during its use for cooking. I generally ensure that any water used during cooking processes is not discarded as waste, but consumed. Thus any trace elements that have leached into the water are not lost. Rice dishes, casseroles and steaming for example are methods I would consider adequate.
Mike

 

[djs]

Using RO for washing up and a shower should be ok but is not ok for drinking or cooking with

What? Really? Many (maybe hundreds of) boats cruising full,time in places like the Bahamas and S pacific use water makers for all their water. It’s worth keeping in mind that the WHO class drinking water with up to 300ppm of dissolved solids as “excellent” quality. Most watermaker users get product water at between 150 and 250ppm.

the article you linked to is talking about water at <50ppm and distilled water has a ppm figure of <0.5ppm.

The negative health effects of consumption of very low TDS water may be real in theory but in the real world, water maker water is fine and, as the linked report does admit, water is only one source of the minerals we need to stay healthy.

 

[chrishscorp]

Is this a future option ?

Brian

That is an interesting development certainly in somewhere where power is in short supply like on a boat but again will need to be remineralised.

Thank you for the link to the report, of which I was aware. I do feel however that the report contains too many “may” and “could” to be truly conclusive. However, I must apologise if I came over as glib in saying “to taste”. That was not my intent. In recognising that RO water is devoid of minerals it is my opinion that the matter can be addressed during its use for cooking. I generally ensure that any water used during cooking processes is not discarded as waste, but consumed. Thus any trace elements that have leached into the water are not lost. Rice dishes, casseroles and steaming for example are methods I would consider adequate.
Mike

The public water supply in India is not particularly great and in better off households some have gone in for small RO kits to make their water 'safe' but those who are not remineralising it are then ending up ill. The times of India has picked up on it and has run a number of stories/blogs etc.

Using the water that has been used for cooking is good, if there are no minerals in your drinking water the other source you will get them is your food, so by cooking with RO you strip 60% of the minerals out of your food so you would be taking a double hit.

Im not an expert or medically qualified the wife is medical and has dealt with RO plants for 30+ years

 

[Outinthedinghy]

As the OP wants to make their own system for washing purposes I think a beer keg might be a suitable container for making a small settling tank.

Or as someone I know on a boat on the Thames does make a sand filter with gravel and stones at the bottom and use that before putting the water through the cheap polyprop filters.

Otherwise you will overload the filters with silt very rapidly.

At the end of the day if it is DIY and it's for washing and showering then filtering it down to 5 microns and chlorinating it followed by a dechlorination filter could be an option.

That might be the cheapest option. Beer keg to settle water, 3 filters, old shurflo pump to transfer to bulk tank, chlorine tablets in tank then filter chlorine out before use.

I've not tried the dechlorination filter but it seems an option if having a slightly chlorine content is frowned upon by the consumer.

If it is for really small amounts of water you could just fill the keg with a bucket. Buckets are handy things to have around anyway. One of the most useful devices ever invented.

Couple of buckets of water in beer keg. Wait 24h then pump through.

Sorted.

 

[geem]

Why is it not OK for drinking and cooking? I’ve used a RO watermaker for 13 years with apparently no ill effect. I would agree that it is devoid of any mineral content, but that can always be added, to taste.
Mike

If you are using a seawater membrane on your watermaker in seawater, there is no mineral content issue. Thst is misinformation. Saltwater converted to fresh drinking water via RO contains sufficient minerals to not be harmful. Most mineral content we need as humans comes from good diet not the water we drink.

 

[geem]

Using RO for washing up and a shower should be ok but is not ok for drinking or cooking with

We have made 175,000 litres of water with our watermaker over the last few years as liveaboards. We drink it. Lots of Caribbean islands have centralised RO to produce water for their mains water supply. Most cruisers in the Caribbean have their own RO watermaker onboard. It's adds great convenience without the need to constantly look for water.

 

[chrishscorp]

If you are using a seawater membrane on your watermaker in seawater, there is no mineral content issue. Thst is misinformation. Saltwater converted to fresh drinking water via RO contains sufficient minerals to not be harmful. Most mineral content we need as humans comes from good diet not the water we drink.

As I have already stated, most people who cook vegetables throw away the water they are cooked in so the minerals that are leached out of the veg are ditched.
If you then also drink RO water and do not remineralise it you will end up deficient in the worst case your body will start stripping out what it needs from what has been laid down in your body.

That is Misinformation...
Wife deals with 24 RO plants in the UK, ( the last one they set up from new I did the initial load up with the softening salt all 11/2 tons of it) 35 years experience with RO is Senior Nurse Specialist, Your quite right what does she know about it.

 

[geem]

As I have already stated, most people who cook vegetables throw away the water they are cooked in so the minerals that are leached out of the veg are ditched.
If you then also drink RO water and do not remineralise it you will end up deficient in the worst case your body will start stripping out what it needs from what has been laid down in your body.

That is Misinformation...
Wife deals with 24 RO plants in the UK, ( the last one they set up from new I did the initial load up with the softening salt all 11/2 tons of it) 35 years experience with RO is Senior Nurse Specialist, Your quite right what does she know about it.

The WHO produced a white paper on this subject that went in to great detail. You have to be drinking water with a PPM below 50 constantly to be at risk of health issue. This is physically impossible with seawater RO. Typical PPM is 180 to 500PPM.
Your wife may want to read the very detailed report

 

[geem]

As I have already stated, most people who cook vegetables throw away the water they are cooked in so the minerals that are leached out of the veg are ditched.
If you then also drink RO water and do not remineralise it you will end up deficient in the worst case your body will start stripping out what it needs from what has been laid down in your body.

That is Misinformation...
Wife deals with 24 RO plants in the UK, ( the last one they set up from new I did the initial load up with the softening salt all 11/2 tons of it) 35 years experience with RO is Senior Nurse Specialist, Your quite right what does she know about it.

I think you need to get a bit more knowledge on this subject. Low pressure RO used in house holds to clean up dirt 'fresh water' is nothing to do with seawater RO. Fresh water RO works at low pressure and can be mounted under the sink in a house. You can achieve very low PPM with these systems. Seawater RO is a high pressure system and uses completely different membranes. It works at 800psi to remove salt. You cannot get down to the levels of PPM that can cause health issues like you can with the under sink models installed in houses to clean "fresh" water. Quoting what happens with Indian town water is not even close to the issue of seawater RO.
Ask your wife if she know the difference and what PPM level is a risk to health!

 

[oldbloke]

Until quite recently most people drank beer for their daily hydration. May be time to resume.