Watermaker TDS

[a64pilot]

Curious as to what the average TDS people get is. I ask as my old membranes were always below 200 and my new ones seem to run 250ish, today was 258. that’s a calibrated TDS meter, and that matters a lot. I have three, one reads spot on, one 10 high and the third 50 low.
Only one of the three is adjustable and of course it just happens it’s the one that’s correct.

The other item of interest is who makes your membranes I guess, I believe the majority of us are Dow Filmtec ones, but there are I’d guess others as well.

Watermaker brand really shouldn’t have much to do with TDS really so long as it supplies the correct flow rate and pressure it’s a function of the membrane.

Also location will matter as some places have higher salinity than others, and temp as well.
There is a poll that should gives us some answers I hope

[jkleins]

Mine have run 230-280 since new. Pretty consistent in the ocean but lower in the Chesapeake.

[RickG]

We are in the Caribbean, US Virgin Islands. We see 170-180 ppm on our Rainman MK II with a COM 80 TDS meter. The membranes are DOW Filmtec SW30 2540. The unit is a year old and these are the original membranes.

Cheers, RickG

[Smokeys Kitchen]

My TDS from a Spectra 150 is @ 140 - 160 measured by the inline TDS probe as well as a calibrated separate meter that I check the feed into the tank manifold with. Unit is @ 8 years old and I believe the membranes are original. Cruising area is PNW

[newhaul]

170 to 180 ppm calibrated band meter .
PMW waters never above 65℉
Powersurvivor35 older membranes.

[Tellie]

You will see different TDS readings depending upon temperature and salinity of the intake water. You will also see different TDS readings depending upon the watermaker used. You will see different TDS readings depending upon the age and condition of the watermaker and membrane. You will see different TDS readings upon some owners desire to set their own pressure settings if adjustable. You will likely see different TDS readings taken in the same spot 20 minutes apart. You will see different TDS readings with identical watermakers working right next to each other in the same intake water and same settings and pressures. You will also see different TDS readings depending upon the accurate calibration of the TDS meter used to read the product. You will see different TDS readings depending on the manufacturer of the membrane itself. And the fun one, and I don't care who says different, even the manufacturers themselves, "every" membrane, even the ones from the same roll, will be different than the next. Though this is a fun exercise for some of us, asking what others TDS readings are is like asking why you get better gas mileage from your new Hemi Charger than your 17 year old son does.

[newhaul]

Originally Posted by Tellie

You will see different TDS readings depending upon temperature and salinity of the intake water. You will also see different TDS readings depending upon the watermaker used. You will see different TDS readings depending upon the age and condition of the watermaker and membrane. You will see different TDS readings upon some owners desire to set their own pressure settings if adjustable. You will likely see different TDS readings taken in the same spot 20 minutes apart. You will see different TDS readings with identical watermakers working right next to each other in the same intake water and same settings and pressures. You will also see different TDS readings depending upon the accurate calibration of the TDS meter used to read the product. You will see different TDS readings depending on the manufacturer of the membrane itself. And the fun one, and I don't care who says different, even the manufacturers themselves, "every" membrane, even the ones from the same roll, will be different than the next. Though this is a fun exercise for some of us, asking what others TDS readings are is like asking why you get better gas mileage from your new Hemi Charger than your 17 year old son does.

but the big question is can I use an off the shelf membrane or am I screwed into the proprietary units . ( I have a spare manual survivor that needs a membrane)

[a64pilot]

Originally Posted by Tellie

You will see different TDS readings depending upon temperature and salinity of the intake water. You will also see different TDS readings depending upon the watermaker used. You will see different TDS readings depending upon the age and condition of the watermaker and membrane. You will see different TDS readings upon some owners desire to set their own pressure settings if adjustable. You will likely see different TDS readings taken in the same spot 20 minutes apart. You will see different TDS readings with identical watermakers working right next to each other in the same intake water and same settings and pressures. You will also see different TDS readings depending upon the accurate calibration of the TDS meter used to read the product. You will see different TDS readings depending on the manufacturer of the membrane itself. And the fun one, and I don't care who says different, even the manufacturers themselves, "every" membrane, even the ones from the same roll, will be different than the next. Though this is a fun exercise for some of us, asking what others TDS readings are is like asking why you get better gas mileage from your new Hemi Charger than your 17 year old son does.

Tellie. I know your very much an expert, I was trying to get a feel for what “average” was.
As I said identical watermaker, last years TDS was always below 200, this year new membranes, always well above 200 with mid 250’s being average.

That has to be a manufacturing variation in membranes, I don’t know if I have one really high membrane and one low, or two high.

I suspicion my new ones are at the higher side of acceptable for a new membrane, and my old ones were are the low end of acceptable, low meaning good in that case.

So I was curious as to how much variation there is in watermakers that are in service.

TDS of the source water will of course affect product output and TDS, but average user can’t measure that, so I didn’t ask it.
Water temp will also affect TDS and output, and most of us know the water temp, so I asked that.

So it’s not really asking why a kid gets lower mileage in a car than you do, as you can control that, while I don’t think TDS is really controllable is it? Sort of what it is, is what your going to get. There aren’t any tricks you can do to lower it?
Does higher pressures mean lower or higher TDS? I mucked around with that last year and didn’t really see a difference.
My old membranes suddenly dropped significantly in output, but TDS stayed the same, tried cleaning them etc., no change. So I upped pressure to 900ish from 800 to recover output and didn’t notice any increased TDS.

I replaced them thinking something had happened to them and better get new ones before they failed was all.


I was also wondering how many were out there with higher TDS, say as in over 400 but were still being used.


So how does a membrane die? From increasing TDS, or from decreasing output? Or either one?
Is death usually sudden or do they die a slow death giving you plenty of time to plan on a replacement?

I’ve discovered that carrying a membrane in spares isn’t probably viable as they have a one year from manufacture shelf life, now they may last longer, but I believe the recommendation is one year.
It’s also I found out a reason to be careful of where you buy a replacement membrane, as apparently there are quite a few out of date ones out there being sold at a good price on Amazon and I’m sure EBay.

[a64pilot]

The Elephant in the room however is I believe, how high a TDS can you have before it becomes unhealthy?
I know I can find sources on line that says up to 500 is OK and that many drinking water sources are higher than that.

But what makes up the dissolved solid, surely has to matter doesn’t it?
A TDS of 500 with the majority of the dissolved solid being Calcium Carbonate because your aquifer is limestone is surely different than watermaker product water from the sea, where surely most of the dissolved solid is Sodium Chloride?

How much sodium until it’s bad for you?


Of course I could be completely wrong, maybe the TDS of watermaker product water isn’t salt, maybe it’s something else?

[belizesailor]

Originally Posted by a64pilot

The Elephant in the room however is I believe, how high a TDS can you have before it becomes unhealthy?
I know I can find sources on line that says up to 500 is OK and that many drinking water sources are higher than that.

But what makes up the dissolved solid, surely has to matter doesn’t it?
A TDS of 500 with the majority of the dissolved solid being Calcium Carbonate because your aquifer is limestone is surely different than watermaker product water from the sea, where surely most of the dissolved solid is Sodium Chloride?

How much sodium until it’s bad for you?


Of course I could be completely wrong, maybe the TDS of watermaker product water isn’t salt, maybe it’s something else?

Short paper on the subject by WHO:


https://www.researchgate.net/deref/h...cals%2Ftds.pdf


Bottom line is up to 1,000 ppm is deemed "acceptable", but no concrete data/studies on health effects of long term consumption of water in the 500-1000 range.

Above 500 some people can start to taste it. My wife has uber sensitive taste/smell...I dont need a TDS meter...I married one!

Here in the warm waters of the W Carib my average is about 250 PPM.

[Bill O]

Originally Posted by a64pilot

Curious as to what the average TDS people get is. I ask as my old membranes were always below 200 and my new ones seem to run 250ish, today was 258. that’s a calibrated TDS meter, and that matters a lot. I have three, one reads spot on, one 10 high and the third 50 low.
Only one of the three is adjustable and of course it just happens it’s the one that’s correct.

Just curious on how do you calibrate your meter? Agree that a calibrated meter is the way to do it and would be difficult to compare tds data w/o an accurate meter. Even "factory calibrated" instruments can be off and should be checked.

Most of the normal calibration stds I've seen for sale are 1,000 ppm which is great if that's your target level. Single point calibration is ok, but in this case maybe ~250 (or lower) would be a better concentration to calibrate for a single point. Ideally you'd want to test your meter through a variety of concentrations through the range you are testing to see the deviation at the different levels. This is the better scientific way, but typically beyond the means for most.

[a64pilot]

Originally Posted by belizesailor

Short paper on the subject by WHO:


https://www.researchgate.net/deref/h...cals%2Ftds.pdf


Bottom line is up to 1,000 ppm is deemed "acceptable", but no concrete data/studies on health effects of long term consumption of water in the 500-1000 range.

Above 500 some people can start to taste it. My wife has uber sensitive taste/smell...I dont need a TDS meter...I married one!

Here in the warm waters of the W Carib my average is about 250 PPM.

Pretty nearly certain that article doesn’t differentiate as to what constitutes dissolved solids, it could and likely is anything that will dissolve in water, and I believe really is geared towards normal drinking water sources, lakes, Wells etc.
Not desalinated water. Ocean water I believe is something like 35,000 PPM of dissolved solids, with I assume, that’s assume not know that a large portion of that is sodium chloride.
So we reduce 35,000 down to 350, a major miracle that I’m not disparaging, but I’d guess that the amount of sodium in desalinated water with a TDS of 350 is likely a lot higher than that of Fl spring water with a TDS of 350.

Could well be a whole lot of nothing as I’m no medical professional, just I’m postulating that maybe there is a difference in dissolved solids, depending on what that dissolved solid happens to be.

I was just curious as to what the average TDS of the average cruisers watermaker was, as I had sub 200 and now with brand new membranes I have mid 200’s

I do not think the brand of watermaker has anything to do with it either, the difference is I believe within manufacturing tolerances of Dow Filmtec membranes. I was wondering just how wide are those tolerances?

So don’t think I’m disparaging anyone, particularly any watermaker, I’m not. Was just typing to educate myself as to what is normal or average of you will.

When I first commissioned my new membranes and tested the output expecting some real low number, cause you know they are brand new and getting mid 200’s, I took the membranes back apart to make sure I didn’t have one in backwards, which I didn’t so I inspected the O-rings, couldn’t find any fault, so I replaced them anyway, put everything back together tested them again and got the same result and called my Watermaker manufacturer saying I have very high TDS, told him what I had done and asked what could be wrong.
I was told nothing is wrong, many have higher TDS than you, you don’t have anything to fix.

See I had become accustomed to 150 ish as normal, so when I saw 100 higher I thought that’s bad, so I got to wondering what normal is.
So I started this thread to try to see what average is, is all.


By the way, my Wife doesn’t like the new water, she says she can taste it, it’s not as good as it used to be, so your not alone.

[Sailmonkey]

Our Schenker watermaker produces 330-350 ppm using a pair of 21” AMI membranes.

The manufacturers design spec for the machine is 300-500 parts, so I’m ok with it and it tastes a million times better than water from just about any dock I’ve gotten water from.

My TDS meter was around d $12 dollars on amazon.

[belizesailor]

Yes, the article is more general.

In warm waters what I have seen, across multiple boats/water makers, is 200-300. Tellie likely has a broader sample to draw from.

[Tellie]

Originally Posted by a64pilot

Tellie. I know your very much an expert, I was trying to get a feel for what “average” was.
As I said identical watermaker, last years TDS was always below 200, this year new membranes, always well above 200 with mid 250’s being average.

That has to be a manufacturing variation in membranes, I don’t know if I have one really high membrane and one low, or two high.

I suspicion my new ones are at the higher side of acceptable for a new membrane, and my old ones were are the low end of acceptable, low meaning good in that case.

So I was curious as to how much variation there is in watermakers that are in service.

TDS of the source water will of course affect product output and TDS, but average user can’t measure that, so I didn’t ask it.
Water temp will also affect TDS and output, and most of us know the water temp, so I asked that.

So it’s not really asking why a kid gets lower mileage in a car than you do, as you can control that, while I don’t think TDS is really controllable is it? Sort of what it is, is what your going to get. There aren’t any tricks you can do to lower it?
Does higher pressures mean lower or higher TDS? I mucked around with that last year and didn’t really see a difference.
My old membranes suddenly dropped significantly in output, but TDS stayed the same, tried cleaning them etc., no change. So I upped pressure to 900ish from 800 to recover output and didn’t notice any increased TDS.

I replaced them thinking something had happened to them and better get new ones before they failed was all.


I was also wondering how many were out there with higher TDS, say as in over 400 but were still being used.


So how does a membrane die? From increasing TDS, or from decreasing output? Or either one?
Is death usually sudden or do they die a slow death giving you plenty of time to plan on a replacement?

I’ve discovered that carrying a membrane in spares isn’t probably viable as they have a one year from manufacture shelf life, now they may last longer, but I believe the recommendation is one year.
It’s also I found out a reason to be careful of where you buy a replacement membrane, as apparently there are quite a few out of date ones out there being sold at a good price on Amazon and I’m sure EBay.

You know me well enough, my last line about the 17 year old was my usual poor attempt at humor.

But you are asking very good questions. My point, in a nut shell, was the fact that all membranes are different to some extent even in the same roll. It makes it difficult to judge just by the TDS readings the over all condition of a membrane. It's true most reputable watermaker companies will say anything under 500 is good. I believe anything over 500 TDS is usually an indication that something is amiss. But that doesn't always mean it's the membrane. Flows and pressures are important to get accurate. As you know a feed pump that is giving issues will effect the TDS readings of a membrane. Fix the feed pump in time and the TDS reading will most likely return to normal. Charting your TDS without charting the flows and pressures as well only gives you one third of the equation. Temperature and salinity of course make a difference. But salinity of the water you're floating in is also a number that needs to be known. This requires a more sophisticated meter that can read accurately such high salinity content which most typical cruisers are unlikely to have due to the cost. As you mentioned, your older membranes were producing a lower TDS reading than your new ones. I see this all the time. This is not an indication that your new membranes are not as good as your older ones or that they will fail sooner. Most likely the new ones will last longer than the older ones even though the older ones are making better quality water. Which leads the question of failure. It is very rare for a membrane that is properly being taken care of to fail catastrophically. They usually slowly fade away as the TDS readings increase over time. Charting the TDS readings as you do is the best way to determine in a good working system if the membrane is starting to show signs of deterioration. A lot depends on where you are cruising. A membrane in the Pacific will usually perform better than the same membrane in the Atlantic. We see some of the saltier waters in the world here on the Atlantic side. The salinity here can range from 32,000ppms to 36,000 ppms. So a difference in product water of 100-150 ppms +/- is an infinitesimal difference really and I wouldn't flinch on the difference if analyzing a system. Also cleaning a membrane in my opinion is a waste of time. Most membranes I've tried to clean over the years were unsuccessful and those that did show improvement had a very short life soon after cleaning. Today most standard membranes are cheap enough and replacement is a better idea and investment on your time. Running your pressures up to 900psi is not a good idea either. Yes this can certainly lower the TDS readings and even increase production but at these pressures and above you risk scaling and slowly damaging your membrane leading to an earlier death sooner than later. You are also correct on carrying a spare membrane. The self life of a membrane outside of a working watermaker is usually a little over a year or so. By the time the membrane in the system goes bad a few years down the road the spare membrane is worthless as well. Yes there are a lot of $200 membranes out there for sale on Ebay and such and there is absolutely no way to know what you are getting. The term "New Old" comes up a lot and they should be avoided like the plague. Unfortunately, there are still systems out there that use proprietary membranes and people with those systems are stuck many times with the higher cost of membrane replacement.



PS, There is some truth to the 17 year old. My Dad bought a new Cuda when I was in high school that was special ordered by someone else and the deal fell through. He got a really good price on it and decided on the Cuda instead of the station wagon he was going to get. He came home with it and asked me what a 426 Hemi was. We got a new station wagon about the time I turned 18.