Water maker - why discard intial water?

[Caroline Joan]

Can anyone tell me why you have to discard the first few minutes of water produced by your water maker?

All I can think of is that it may not be working properly & contains high level of salt?

So do you do a taste test before putting it into your tank?

[Sojourner]

I'm not well versed (yet) on my watermaker, but I know this: ever smell the fresh toilet seawater you flush that sits in the pipes after not being on the boat a week or two? That's also in the watermaker. I do flush the WM with a bit of fresh water after every use, but a proper flush takes a lot of liters. The first minute or two of running it is flushing itself, then when you run the pressure up and you won't clog the membranes as quickly (I think). And yeah, although the machine is smarter than I am, I do take a little shot glass and pull a shot from the outflow pipe before it enters the tank, luckily in the galley sole bilge. Doubt I need to, but with only 1 giant tank, I don't want to risk filling it with bad water...

[Dulcesuenos]

You should use a TDS meter and test your water before switching to tank. Those cruisers I've worked with who did the "taste test "only ended up drinking alot of water over 1000 ppm tds. It takes 2 to 3 minutes for many watermakers to clear the brine and get proper product water from their membranes.

[Bruce Beard]

The water that comes out of a water maker just after starting is both high in salinity and disgusting smelling.
On our previous boat, we used a Spectra Catalina 300 that utilized strictly manual valves. I plumbed the output to a y valve with one output to the tank and one to a small faucet that emptied into a sink. It took about 4 or 5 minutes for salinity to begin dropping and a good 10 minutes of running to get the smell gone.
The thought of that smell getting into our fresh water tank is appalling...
On our new trawler, we have a much larger 120 volt water maker with automatic changeover valves. The output is much higher on this machine and the entire process happens in just a couple minutes.
It smells better too... I suspect that is simply a matter of water volume.

[Tellie]

Originally Posted by Bruce Beard

The water that comes out of a water maker just after starting is both high in salinity and disgusting smelling.
On our previous boat, we used a Spectra Catalina 300 that utilized strictly manual valves. I plumbed the output to a y valve with one output to the tank and one to a small faucet that emptied into a sink. It took about 4 or 5 minutes for salinity to begin dropping and a good 10 minutes of running to get the smell gone.
The thought of that smell getting into our fresh water tank is appalling...
On our new trawler, we have a much larger 120 volt water maker with automatic changeover valves. The output is much higher on this machine and the entire process happens in just a couple minutes.
It smells better too... I suspect that is simply a matter of water volume.

If any watermaker smells bad on start up the most likely culprit is that the fresh water flush is not set up properly.

[mvmojo]

Use a TDS meter. You'll see that the early output has a high level of total dissolved solids (salt) and that it decreases to "safe to drink" levels over a short period of time. It's generally accepted that <500 ppm TDS is "safe" but does have a slightly salty taste. <300 ppm tastes pretty good, and <100 ppm seems to have no taste at all. Our product water is generally around 120 ppm a minute or two after startup. I've never had a problem with product water smelling, which is caused by bacteria growing in the plumbing and on the membrane. I fresh water rinse the membrane and plumbing for 60 seconds every time I run the watermaker. We make 33 gph and I usually run it for 2 hours so using a couple of gallons as a rinse is only about 3% of total product.

[lordgeoff]

Originally Posted by Caroline Joan

Can anyone tell me why you have to discard the first few minutes of water produced by your water maker?

All I can think of is that it may not be working properly & contains high level of salt?

So do you do a taste test before putting it into your tank?

The first 5 minutes or so is a rotten egg smell as the system clears itself of salt water that has been in the filters and pipes etc. Ours (Spectra 150) came with an Electronic water tester. Smell and taste test works fine but the tester is good as it gives ppm solids in the water. We keep water as high as 500ppm but usually it is around 200ppm.
We keep the Desal water in separate containers for drinking usually but can divert it into the tanks if they are running low. We don’t backwash the water maker as we use the water maker usually each Friday. Pickle when we leave the boat. Currently pickling with Glycol. Seems to work fine. The water maker is 5 years old.

[Tellie]

Again, if you are smelling bad product water (Rotten egg smell) on start up then your fresh water flush system is not set up correctly.

[Paul L]

Originally Posted by Tellie

Again, if you are smelling bad product water (Rotten egg smell) on start up then your fresh water flush system is not set up correctly.

Or you aren't using it.

[lordgeoff]

Originally Posted by Tellie

If any watermaker smells bad on start up the most likely culprit is that the fresh water flush is not set up properly.

Regardless of whether you flush the water maker or not there is salt water sitting in filters and piles before entering the water maker. As we all know salt water sitting for any time gets smelly.

[a64pilot]

Originally Posted by lordgeoff

Regardless of whether you flush the water maker or not there is salt water sitting in filters and piles before entering the water maker. As we all know salt water sitting for any time gets smelly.

On mine the fresh water flush, flushes The filters, the membranes and the HP pump as well as the low pressure boost pump and lines.
Only salt water in the system is from the thru hull to the panel.

At least I think so anyway

[Dulcesuenos]

If a fresh water flush system is setup correctly you can flush out the intake line completely by also flushing water backwards through the line and thru hull

[lordgeoff]

Originally Posted by Dulcesuenos

If a fresh water flush system is setup correctly you can flush out the intake line completely by also flushing water backwards through the line and thru hull

Yes of course you can if you want to go to the trouble. Me? I like to keep it simple.
Once a week I run the Desal and make the drinking and cooking water I need.
The Desal goes into my 25Lt containers. When they are full I turn the Desal off.
I then go to the fridge and snap the top off a beer...........
Repeat every Friday just before sundowners.

[Tellie]

Originally Posted by lordgeoff

Regardless of whether you flush the water maker or not there is salt water sitting in filters and piles before entering the water maker. As we all know salt water sitting for any time gets smelly.

Not to beat a horse here, but as Dulcesuenos correctly points out, If the flush system is set up correctly it will flush the filters and lines as well so there is no salt water left in the system to go bad. The rotten egg smell is hydrogen sulfide gas. This gas can seep by a salt water membrane and make the water smell bad. This is why a proper flushing is important. Once you have a system that starts to bio-foul, and that's what this is all about, it can set in and be tough to get out without a chemical cleaning. It's not difficult to set a fresh water flush system up correctly, but it should most definitely be done. A consistently fouling system can and will lead to other issues and costs as well.

[Bruce Beard]

Originally Posted by Tellie

If any watermaker smells bad on start up the most likely culprit is that the fresh water flush is not set up properly.

It flushed just fine. Lots of fresh water that got to everywhere it was supposed to for the correct amount of time. I always felt it was a function of the salt water left inside the filter housings after the flush. There is always some left in the housings at the bottom no matter how long the flush lasted.
I was initially concerned but Spectra assured me it was normal for my system.
Something must have been happening as the membrane was still working just fine at 11 years old. No degradation of water volume or quality.
Every time I changed a filter on that system I was amazed by the foul smell.
Interestingly, the US Watermaker 800 GPD watermaker on our new boat never smells the way the Spectra machine did.
Even when filters clog and the machine is stopped to change them without a flush they never smell that bad...