RO(DI) experiences with Ottawa City water

[mchotdog]

whats the city's water TDS without treatment? what is the phosphate and nitrate level?

[fischkopp]

Take a look at the Detailed 2010 Britannia Purification Plan Drinking Water Quality summary:
http://www.ottawa.ca/env_water/water_sewer/water_wells/wells/city_wells/britannia_en.html

Conductivity is 159us; that will translate to 80 ppm on most TDS testers.

[Rybren]

Yup, the last time I checked my tap water it was 85.

[Hookup]

Thanks everyone for their input!

It looks like getting the TDS down to 0ppm isn't a a problem if the RO unit has DI. That's good!

I read a bit up about the cold/hot water issue. With increasing temperature, the holes in the membrane will expand, allowing more water to pass through. But the bigger holes also allow more impurities to pass. Hot water is said to damage the membrane. For best RO water it's recommended to use cold water.

I didn't think about chloramine. Do you trust your RO/DI to remove it or do you still add a bit of prime to be on the safe side?

Id like to see that information if you can post it please.  I think defining hot and cold is an issue that first needs to be cleared up.  there's a difference between 70degrees and 100degrees... HOT water is likely bad and it would hold higher TDS due to the excited state of the water... and i can see it expanding the membrane... but 70* is not really hot water, it's just not cold...

i can see how cold water, like 40* water would shrink holes in the membrane and create a significant waste to clean water ratio increase under the same principal that hot will allow more tds thru the membrane.

I wish I could say this is why I believe that 65-70degrees is the optimum temp for the water, but really its just some rumor I picked up along the way...  

[ray]

I was jnformed that membranes when rated are measured at approx 60 PSI and 70 degree F water temp.So if yoiu are looking for optimal output according to membrane output these are the numbers you wish to have.

Ray

[fischkopp]

Id like to see that information if you can post it please.

It's from a German site: http://www.drta-archiv.de/wiki/pmwiki.php/TechnikOsmose/Wassertemperatur

It sounds like in the end it pretty much depends on the quality of the membrane. I wouldn't be surprises if the membranes that we get today are less susceptible to temperature differences, whereas a decade ago these rumors were actually true.

[Rybren]

Perhaps, but there is a vastly different level of performance in my system in the summer versus the winter.  Production really drops in the winter.

From the Alberta Government website:

Temperature

The optimum water temperature for most reverse osmosis membranes is 25°C. As the temperature drops to 5°C the capacity of the reverse osmosis unit will be reduced to less than one half. Long, small-diameter water feed lines will allow the water to warm up to room temperature (20°C) before reaching the membrane. This will increase treated water production.

Here's the whole article...

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex5432

[Hookup]

I was jnformed that membranes when rated are measured at approx 60 PSI and 70 degree F water temp.So if yoiu are looking for optimal output according to membrane output these are the numbers you wish to have.

Ray

This is spot on with what I believe to be true, but I got nothing other than a quote from Ray to back it up.   But really, who needs more than that?  Thanks Ray!  Lol

[delslo]

While we're digging up research info. Here is a related question


How come tap water doesn't have copper in houses that are all copper plumbing?  I'd think trace amounts would build up over months if not years then.

The reason that there aren't trace amounts of copper is that the tap water isn't acidic enough to cause the degradation of the copper pipe. If provide enough time, a month (just a guestimate), you would most likely find trace amounts of copper in the initial bit of water coming out of the pipe, but after a few minutes this would clear. The lead solder once used followed the same situation, except that it is more reactive and thus degrades/leaches faster, overnight non-use and you would find trace amounts.