I have a water company and my water TDS are getting very its 160 coming, I want below 120 so how can I do this?

TDS of is in the very good range and does not have any objections for its use even for drinking. as per US EPA upper limit is mg/l. even less TDS in water has many ill effects. less TDS effects waste taste and even it may lead to corrosion of pipes. So I prefer dont invest much just to reduce a mg/l. But Still for some reason if it is required to reduce the TDS then one can go these technologies

RO- Reverse osmosis- Remove the dissolved minerals by forcing water to pass under synthetic membrane having minute pores.

Electrolysis- getting water electrolysed between cation and anion to reduce the TDS but many things should be considered before doing it.

Distillation- heating the water to vapour. as mineral salts does not vaporize only water will be vapoires and condes back to water. but frequent cleaning in very much necessary

Deionisation- well I dont have much idea regarding this technology but it is also one the recent technology used to reduce TDS. 

Try to pass the TDS water again to your water treatment plant and check TDS. It will become less than. However TDS water is fit for drinking. WHO recommends less than TDS fit for drinking.