I see lots of questionable advice here.
For one you will not see any more pressure at the washing machine than you will at any other faucet in the house unless you have a pressure regulator somewhere. The pipes are all connected together so its the same through out. Installig a gate valve does not raise pressure. What the person showed this poster was in high flow conditions restricting the flow did raise the pressure back closer to the static pressure but you cannot raise it above that point. A RO/DI uses about one quart of water per minute tops including waste and treated flow combined so that flow will have little effect on pressure. If I stuck the RO membrane on a hose with an open end then yes plugging that open end would get the pressure back closer to static conditions.
Most domestic well systems are set at about 30 psi which is sufficient for most household use but too low to run an RO membrane with any level of efficiency. 40 psi is about the bare minimum and 60-80 is preferred.
You want the pressure gauge after the carbon block but before the RO membrane so you are measuring the pressure available to the membrane, this also gives you an indication of prefilter andcarbon fouling or plugging if you have sediment of particulate problems.
A booster pump is a wise investment if you have low pressures as it will greatly increase the RO rejection rate or removal efficiency and make your DI last many times longer.
Warming the water is not wise for a couple reasons. Remember being in the shower and someone started the washer on cold or flushed the toilet? You got your tush scalded and thats the same thing that happens to the RO membrane. Membranes cannot tolerate anything over 113 degrees or it will melt the thin plastic membrane fabric alsmot immediately. Also cold water treats better than warm water since it is more dense or less viscous. It will give you lower TDS from the membrane than warm water at the same pressure. Always take increased pressure over warmer water. The Aquatec 8800 is the best booster you can buy. Make sure when you are comparing prices that the 24v DC power supply and pressure switch is included, some price it seperately so get you in the end.
Again a 75 GPD RO membrane usesabout a quart a minute so open the ball valve or inlet valve all the way. There is really no such thing as too much pressure on a RO membrane, they are rated at over 150 psi working pressure and higher. I run my booster between 90 and 100 always to get the best rejection rate and production.
Handheld TDS meters are much preferred over inlines. The inlines are not temperature compensated so can be as much as 2% off for every degree C difference between the air and water temperature. The temp probe is actually inside the fat part of the probe behind the little rectangular hole you see so it reads air and not water and they are rarely the same. Plus with the inlines you are dedicated to two points and will not work portable since it needs flow past the probe inside the tee. A handheld can measure the tap, RO only, RO/DI, your ATO container, the LFS, the grocery store vending mcahine, your buddies systems etc. Much more handy and accurate too.
Most color changing resins are a rough guide as to condition only. They either turn colors too late, in streaks or layers or not at all. They add dyes to color changing resins which shows up as TDS too if you didn't know that. Always use a handheld TDS meter for low range accuracy.
Many vendors tried the 150 GPD membranes and many discontinued them for several reasons. Spectrapure tried them for a time but could not get ahrdly any of them to pass their quality control checks and rarely did the ygive 98% rejection, most were way low. They also require a minimum of 65 psi to produce anywhere near 150 GPD. Heck i get 120+ out of a 75 GPD Dow membrane at 95 psi and better than 99% rejection. I tried a 150 about 4 years ago and was one of the lucky few who got one that worked. Spectrapure had to tes ta bunch of them before finding one for me. I later sold it though and got a boosted system and am happier.
When checking your TDS alwasy test at three points. Since the RO membrane is the workhorse of the system and does 98% of the work you need to know how well it is performing, you could get 0 TDS final water and the membrane is doing squat making the DI carry the bulk of the load. Test tap water TDS and RO only TDS to calculate your rejection rate then take the RO/DI TDS to check your DI resin condition. Something to keep in mind is for every 2% you can increase your membrane efficiency or rejection rate, you will DOULBL the life of your DI resin. An efficient membrane or booster pump will pay for itself quickly if you make much water at all in DI savings alone.
