Please remember, the sediment filter and carbon block have very little to absolutely nothing to do with TDS, the yare there to protect the RO membrane from sediment, particulates, colloidal materials and chlorine. The former are measured in microns and up to visible with the human eye or about 40 microns down to maybe 1 micron or in some cases 0.5 microns. The latter, chlorie is usully present at around 1 ppm or mg/.L so would be 1 TDS.
TDS or dissolved solids are just that disslved in the liquid not suspended and in the 0.0001 micron range, many many times smaller.
The RO membrane is the most expensive piece of the system and the workhorse, removing 90 to 98% of the TDS, it makes no sense to not change filters when their sole purpose is to protecdt it so it can do its job efficiently. Dirty filters reduce pressure to the membrane making it less efficient and reducing DI life if you have DI, costing you money and lower water quality. Your reef suffers.
What do you gain?
I just know you hunt for these kind of posts!! LOL
Its the one subject I am pretty knowledgable about!
The RO membrane will go on being efficient until it fails. You will either see a sharp increase in TDS meaning the TFC fabric has ruptured due to too much solids build up causing it to find a wek spot and tear, or you will see a decrease in GPD which is often the case or possibly a combination of both. Again the sediment and carbon have little to do with TDS so you monitor their conditions using a pressure gauge or gauges before and after such as I do and a low range chlorine test kit. TDS readings don't tell you anything about their condition.
Its the one subject I am pretty knowledgable about!
The RO membrane will go on being efficient until it fails. You will either see a sharp increase in TDS meaning the TFC fabric has ruptured due to too much solids build up causing it to find a wek spot and tear, or you will see a decrease in GPD which is often the case or possibly a combination of both. Again the sediment and carbon have little to do with TDS so you monitor their conditions using a pressure gauge or gauges before and after such as I do and a low range chlorine test kit. TDS readings don't tell you anything about their condition.
Total Dissolved Solids. Its a measure of all things electrically conductive in the water, solutes or contaminants.
TDS is not a measurement of anything specific but it is easy and inexpensive to test and is a very good indicator or water purity.
The other measurement is TSS or Total Suspended Solids, big stuff suspended not dissolved in the water. Things like sediment, silt, grit, sand, particulates and colloidal materials. These are the reason you have a sediment filter at the beginning of the process so they do not foul or plug the carbons pores where chlorine is adsorbed and the RO membrane where the TDS is removed. Two different processes and two distictly different physical sizes or materials. One can be visible with the human eye, TSS while the other is down to the atomic level or 0.0001 microns.