the only way to test for total disolve solids is with an electronic tester this will test for the conductivity of the water itself so electronic metor like this Hawk multi2 will give you total disolve solids and parts per thousand this particular pool has 1.53 parts per th which is 1500 parts per million so what TDs is or total dissolve solids is the accumulation of conductive chemicals in the water particularly after the water evaporates and there's no fresh fill water this will include calcium hardness alkalinity ceric acid chlorides bromides sulfide silicates and all their chemicals and organic compounds found in the water basically total disol of solids is everything in your pool besides water itself H2O the ideal level of total dissolve solids is 1,000 2,000 parts per million if you have anything over 2500 parts per million your water in your pool may be experiencing some problem so if your total Sol solids is too high in your pool you may have cloudy pool water your pool may have scale in it you may have algae blooms for no reason with high chlorine levels may have a salty taste and you'll have an increased amount of bacteria in the water along with accelerated wear of the plaster the only way to solve a high total dissolve solid level is to drain the pool partially or completely if you can't drain your pool because of water restrictions you can run your pool longer that will help combat some of the problems that are associated with total dissolve solids at high levels since the meter uses the conductivity of water to measure the total dissolve solids the saltwater pool since a lot of salt in the water it's going to have a high total disolve solid reading there's really no way to get a exact total dissolve solid number in a saltwater pool but there's a rough formula you can use you just take the salinity reading and you subtract it from the total to solve solid reading the salinity reading at this pool is 3.57 parts per th000 which translates to 3500 parts per million see the total result Sol is is high in this one also it's at 5,000 parts per million so for this pool I took the TDS of 5,000 I subtracted a solinity of 3500 and I got a total disolve solid of 1,500 parts per million so again total sub of sols will run high in a saltwater pool don't be alarmed that's cuz of all the salt and the water for spa you want to get a sample of your fill water you want to make sure that your total dissolve solids is no more than 1500 parts per million and above with the FI water total dissolve solids is so this here the fill water is less than 1,000 parts per million so the maximum for a spa with this fill water would be 2200 parts per million since a spa is such a small body of water and usually there's a lot of chemicals used in it you want to take a sample of your fill water get the TDS from that you want to add 1500 parts per million to it so the maximum would be your fill water TDS plus 1500 parts per million so to maintain fresh clean water in your pool it's important to test for total disol of solids in your water