Spectrapure 90gpd Piggyback

[chrisely24]

I had to order replacement filters for my SP 90gpd so I went ahead and ordered the piggyback kit also.

I finally got around to actually doing some math today. Right now with a 100psi booster pump and 50psi reading on the dial using the full length of flow restrictor that came with the kit, it is making 196gpd at a ratio of 2:1.

I contacted Spectrapure and they said to start cutting the flow restrictor 1" at a time until I reach a 3:1 ratio.
I will try and do that tomorrow, I hope it doesn't cut my GPD down too much. I would hate to have to spend another 100 bucks to buy a new pump.

 

[pegasus]

http://www.f3images.com/IMD/UserManuals/YSP5151.pdf. In this chart, it says:

Collect waste water (yellow line) and product water (blue line) in a measuring cup for 1 minute each. You
should be producing 4X more waste water than product water. If your system is producing less than a 4/1
ratio, you will need to adjust the flow restrictor (capillary tube that was inserted into the waste line).

On the other hand, the chart also says to remove 3" of flow restrictor if your product rate is 163gpd, 2" of flow restrictor if your product rate is 175gpd, and 1" if your product rate is 186gpd. Based on the chart trend, if your product rate is 196gph, you should have to remove 0" of flow restrictor. Another thing to consider is the addition of the booster pump. Booster pumps increase membrane efficiency, sometimes as much as 100%. That doesn't mean that a membrane rated at 90% rejection rate will suddenly reject 180% TDS, it simply means that a membrane operating under low pressure may go from 45% rejection to 90% rejection. Sorry if I lost you on that one...

I find 4:1, and even 3:1 an exorbitant amount of waste water, but then again, I'm not familiar with Spetrapure. I started with a 3:1 ratio with my 100gph RO/DI, but after adding a (up to) 100psi booster pump, I'm getting a 1:1 ratio @ 50+psi (open flow). If you have a TDS meter before and after the RO membranes, I wouldn't worry too much about what the chart recommends. As long as the rejection rate matches what the membranes are rated for, then there shouldn't be any issues. For instance, your membranes are rated for a 90% rejection rate (each), and your TDS is 200ppm on the inlet side of the RO, and the TDS is 20ppm on the product line, then your membranes are working at maximum efficiency. Just my 2c...

 

[chrisely24]

Thanks for the writeup. Tech support had me move the incoming tds probe to somewhere in the the system after the membrane so he could see what the output there was. It reads 3 and the total output product water is at 0. He said if it starts climbing from 3 then the membranes are wearing out.

I don't have to make tons of water but when I do run it, it will be nice to have it done a lot quicker