Should I buy a booster pump?

[phaze5]

Ok got a ro unit for free, yeah for free. I replaced all of the filtlers (membrane, di, carbon, and sediment). I also put a 100gpd flow restrictor on the discharge line. Now I just turned the thing on (from being dry) and in 2 hours I have less then half a 5 gal bucket (about 2 gals). Now if I did my math right at a inlet pressure of 30-40psi, I should be getting 4.16 gals per hour. Looks to be I am getting 1 gal per hour. Should I wait and let the membrane "settle-in" or should I buy booster pump? I dont know my inlet pressure as of now but I am going to buy a pressure gauge.

[franklypre]

I would give it a day or so, not sure about discharge restrictor sounds like if only 100 gallons is allowed to be waste water than you can only hope to get about 50 of RODI water.

[AZDesertRat]

First and foremost, i hope you did not install a Dow Filmtec 100 GPD membrane. They are the worst possible choice since they are actually a 90% efficient nano filter membrane and not a 96-98% efficient RO membrane.

This makes a huge difference when it comes to final wate rquality and DI resin life since for every 2% you increase the RO membranes efficiency you DOUBLE the life of your DI.

 

Anyway, two things have a major effect on GPD, one is incoming water pressure, the other is water temperature. Dow membranes get their manufacturers GPD rating at 50 psi and 77 degrees F water temp. GE Water and Applied Membranes get their ratings at the same 77 degrees but require 65 psi to produce the rated amount. One or the other or both will raise or lower the GPD. To calculate the actual GPD you need to know both the temp and pressure. You also need to know your incoming or tap water TDS and your actual waste ratio, it should be 4:1 but often is much more, especially in winter with colder water. All these things will have an effect on GPD.

 

Too much going to waste reduces the pressure available to the membrane reducing both rejection rate (removal efficiency) and GPD since it is going around the membrane and not passing through it. High TDS causes higher osmotic pressure meaning its harder to squeeze the water through the membrane. Low tap water pressure means less is going through the membrane and what gets through is not being treated as well. Cold water is more dense so again less passes through.

 

A word of caution here, many people attempt to warm the water up by blending or tempering hot and cold water feeding into the membrane from the faucet. BAD IDEA and the quickest way to ruin a membrane. Remember being in the shower and someone flushes the toilet or starts the clothes washer? You got scalded. Same thing happens to the membrane and it cannot take hot water at all, anything over 113 (much less than most hot water heaters are set at) will toast a membrane in a hurry. Warm or hot water also produces higher TDS in the finished wate rso colder water is actually preffered.

 

Boosting the pressure is the best option if production is slow. Yes I would give it a few days to season the membrane but it probably won't go up significantly. If you get a booster, don't cheap out and get the smaller model, it is designed for 25 to 50 GPD systems not 75-100 GPD systems and will not perform well.

 

Unfortunately used systems usually end up costing more by the time you replace worn out components and make upgrades needed to bring them up to a reef quality system. You can get into a brand new 90 GPD reef quality guaranteed RO/DI with a inline pressure gauge and dual inline TDS meter as well as 0.5 micron prefilter, 0.5 micron 20,000 gallon carbon block, batch tested RO membran, capillary tube flow restrictor you trim or adjust to your exact water conditions and ful size 20 oz vertical refilable DI for less than $150.

 

30-40 psi is not sufficient to operate a RO membrane, especially with colder water temperatures too. A 100 GPD Dow membrane at 30 psi and 50 degree water will only produce about 32 GPD best case. If its a 100 GPD GE Water or Applied RO membarne then its down to 23 GPD best case. Take the same two membranes but increase the pressure to 60 psi with the same 50 degree water temp and the production increases to 73 GPD for the Dow and 54 for the GE or Applied. A booster is probably in your future. You are looking at around $125 complete for an Aquatec 8800 with a pressure switch and 24v power supply.

 

Get your actual pressure with the pressure gauge, a temperature with a thermometer and time your waste and treated flows with a measuring cup and clock or watch and let us know what they all are, this wil help with recommendations. If you got a TDS meter that helps too.

[phaze5]

yup its a dow membrane... but I am going to keep that for now, til I have to replace it. The water is cold (about 55 deg.'s). Looks like a booster is it, I was trying to keep the cost down but your right... I have spent a good 85 bucks so far, and looks like a booster is going to put me at about the same about as a new one with out the booster.

 

http://www.dow.com/liquidseps/prod/tw30_1812100.htm

[AZDesertRat]

Before buying the booster you might check out the CSP-DI here:

http://www.spectrapure.com/email/customer-...eciation.html#1

Its only $20 more than a booster and comes with a pressure gauge, TDS meter, capillary tube flow restrictor, vertical DI and more. They sell a ton of systems in NY due to the high sediment loading in the City area. Old pipes and conduits and impoundments with little or no treatment lead to low TDS but high TSS or suspended solids. Their absolute rated prefilters especially the ZetaZorb are the cats meow for situations like that. 10x the surface area so less chance or plugging and less pressure drop so not only better filtration but longer life too.

[phaze5]

unforunatly buying a new unit is out of the question as I have already spent and the unit is now up and running. I'll prob just deal with this for right now and in the future when I buy a house upgrade to a new unit. thanks for showing me that I have book marked that page for later use.