Extremely high tds readings in iowa city area!?!

I don't think that's all that extreme, but there must be something wrong with your RO membrane if you are only getting 170 ppm afterwards. You will burn through your DI in a matter of minutes if that is the case. That is roughly a 70% rejection rate, you should be getting at least 90% rejection.

Do you have it putting out 5 gallons waste water to 1 gallon good water?

 

Well somethings not right. After 120 gallons it should be broken in by now. Are you using a clean cup to take samples? Are you testing after it has been running for awhile?

 

I agree.  Something's definitely not right.  It sounds like the RO membrane is bad/clogged/used up - or you're getting a bad TDS reading out of the RO water.  We have bad water also here in West Des Moines.  The TDS on my input water runs about 500-550.  But the output after the RO membrane has varied from 6 - 15.
As the other reply mentioned, you need to be very concerned about the DI unit, if you are truly getting 170 TDS out of the RO unit.  I just finished changing the resin in my DI unit.  I talked with the guys from Bulk Reef Supply, where I get the replacement resin, about how long the resin should last.  He indicated that about 5000 units of TDS will deplete the stuff.  So, if you're running 170 TDS into the DI unit, theoreticallyl you would only get about 30 gallon of water before it would would be depleted.  Expensive!

 

perfect. It must not have been sealed right.

 

I'de say 2ppm is nothing to worry about.