Watermaker membrane PM?

[Mainstreet]

I have a an older HRO System 9 RO watermaker rated at 20 gallons per hour. Lately I've noticed the TDS value has risen from 145 to 350. Is there a simple cleaning or rinsing process that will bring the TDS value down to its 145 level?
I was wondering if a periodic rinse with distilled or DI water would be of value?

[belizesailor]

How old is the membrane? 350 is still a reasonable range.

A distilled water rinse isnt going to do anything other than maybe temporarily (for maybe a use or 2) drop the TDS. To clean the membrane you will need to use chemicals, but I dont know what is compatible with the HRO system. Maybe someone else can chime in with that.

[Mainstreet]

Thanks for your response. The unit, I believe is from the late 80s or early 90s. It came with the boat when we purchased it a year ago. As to the membrane age, I have no idea so I'm assuming its original. I changed out the filter cartridges three months ago in the pretreatment assembly; it has two of them in series.

[belizesailor]

Wow, then 350 is pretty impressive...enough so that Im skeptical of it being correct. How are you measuring TDS?

[Mainstreet]

I'm using a typical battery powered TDS meter. I've checked it against city potable water and it appears to be within reasonable accuracy.

[Tellie]

Try changing out your prefilters to new ones. If they've been in there for three months they are over due. You may find this drops the ppm readings as the system will flow better. As Belizesailor states, 350 is still a great number. I wouldn't attempt a cleaning at that number.

[travellerw]

Damn.. 350 is fantastic for a unit that old.. Sure our unit made 110 when it was new, but that didnt' last long.. We rose to 200 and stabilized there.

Tellie is the expert for sure.. However, every time I heard of a cruiser complaining about high TDS, the only solution was new membranes. I have never heard of cleaning, adjusting or filter changes making any appreciable difference. However, I'm only going on word of mouth from other cruisers. Tellie has much more data than I, trust what he says.

Again 350 is still a good number and drinkable for sure.

[rabbi]

Maybe something in the seawater?

We had temporary spikes in the TDS (going from 180-200 up to 600) when cruising nearshore in two areas of greece. I suspect there was something other than salt in the seawater that passed the membrane and triggered the TDS meter.

If its a permanent increase it can be a sign of the age of the membrane or possibly a very very small leak from the high pressure side into product water side, an old O-ring for example.

With a watermaker and membran of that vintage I guess 350 is a great number.

[iancoombe]

This maybe a slight hijack but I've ordered a new membrane for my village marine water maker, can I install the membrane without running it as we are on the hard? probably be a month before we can crank it up.
Cheers

[belizesailor]

A dry membrane is a dead membrane. You will at least need to run it enough to flood the pressure vessel.

[rabbi]

i guess the membrane will arrive vacuum packed, so you can keep it like that until you can install and use it.
Or you can install on the hard and pickle with chlorine free water and whatever storage chemical your membrane needs.