Help Please with my Kent Rodi unit

[hugh ngo]

I have a brand new Kent 50gpd rodi unit and when I hook it up to my washer cold side, it doesn't seem to make any water (just drips), but the waste side is coming out normal. Any ideas?

[AZDesertRat]

What is your water pressure and water temperature? Have you used a measuring cup and watch/clock to time both the good and waste flows to see if they are about 4:1, waste to good ratio?
Pressure and temp have a huge effect on output and that is why most people opt for a Dow filmtec 75 GPD membrane or one of its vartants. Some membranes and I bekieve Kent fits into this category, get their GPD rating at 65 psi and 77 degree water temp. So in the case of the Kent if you have less than that on either or both numbers yoy will get significantly less good water, The Dow Filmtec is rated at 75 GPD at only 50 psi and 77 degree water temp so puts out significantly more water even if its cold or lower pressure. The Kent is comparable to a 35 GPD or so Dow and the Dow would put ot 100 GPD at Kents required 65 psi!
The drip drip drip you are getting might equate to 25 or 35 GPD which may be normal in winter time with a 50 GPD membrane and colder water.

www.buckeyefieldsupply.com has a really nice calculator at the top of their home page that will give you a very accurate estimate of expected flows if you know the pressure and temperature of your water.

[hugh ngo]

Makes sense, I might have to switch out membrane. This is winter time, temp. around here it like around 50 degree in the highs. I might have to buy a pressure guage to see what my water pressure is. Thanks for clearing this up, so it wouldn't be worth the money to buy a booster pump either.

[AZDesertRat]

Even with a booster pump the best you could expect would be 50-60 GPD tops. If you had the Dow 75 membrane you would probably see 90-100 GPD with a booster pump. If you are making water andstoring it in a Brute trashcan it may not matter so much, but if you are waiting around for it to make 20 gallons for a water change it seems like an eternity. Another option would be a piggyback membrane system to just about double your production if you have sufficient pressure to do so. With my old 90 GPD MaxCap system I added a second 150 GPD membrane and pushed my production to 240 GPD in summer months and about 200 even in winter. That was at better than 99% rejection rate since the membranes were hand tested and guaranteed 98+% efficient. Well worth the money in my case as we have extremely high TDS and CO2 problems in the Phoenix area and DI does not last long with normal membranes and resin.

[hugh ngo]

For right now I need my Rodi to make 300 gallon. At the rate that my Kent is making, I think it's going to take weeks. What do you think I should do? Should I get that 75gpd membrane? I can almost guaratee that my water pressure is low, until I can prove it wrong, I would have to locate a pressure valve.

[biger]

I called my local water company and asked about the water pressure and they sent somebody out to the house with a meter to measure it for me. I live in a small town tho.

[celano]

Get a pressure gauge and see what kinda output your faucet has. Its cheaper than buying a booster pump and on the off chance you don't need the pump a pressure gauge is a nice feature to have on your unit anyway so no real money lost.

Next if you feel temp might be and issue get a 5gal bucket fill it with water and put a heater in it set to 77*. Go out and get some more tubing for your input line on your ro/di and coil it around and around and around inside the 5gal bucket....the idea is that as your cooler tap water pass' through the warmer water in the bucket it warms up as well. Its works kinda like a radiator on a car but instead of cooling the water like a radiator does you want to heat it up.

These are just a couple options that might save ya some cash. They arnt guaranteed to work but the financial investment is so low that its worth a shot.

[AZDesertRat]

THe heater in a bucket thing does not work all that well. It takes a gob of BTUs to heat one gallon of water even 1 degree. By the time you circulate cold water through it a heater does not keep up well and runs non stop drawing a huge wattage. It sounds good in theory but in practice is not a cost effective option.

[atvdave]

sense I had the day off today and my new capillary flow restrictor was making water at over 20:1 (details in another thread) I decided to try a modded version on the heater in a bucket thing.

My RO/DI unit sets close to my sump area in my cold garage. I went to Lowe's today and got 50' of tube & 2 connectors, total cost around $6.00.

I put the 50' of tube into my sump and ran my supply water going to my RO/DI unit through it.

I let it run for about 30 min's and did some temp reading's.

Tap temp 56 F.
temp coming out of my RO side 68 F.

I have my tank hooked up to controller so I'm going to monitor if my heater kicks on more often than when the RO/DI unit is off. Only time will tell.

12 degree isn't a big difference but maybe it will help make water faster.

[celano]

Atvdave thats pretty sweet that it raised 12*. Did you loose any pressure since you added 50' of line or is it minimal? You also mentioned that your ro/di is kept in a cold garage my your sump. Do you think that if it was inside at 70* it would raise the water temp more?

[hugh ngo]

I was wondering if I could use a 100gpd membrane. Does anyone know if this work with my Kent 50gpd unit.

[AZDesertRat]

Stay away from the Dow Filmtec 100 GPD membrane. It is not a true 98% rejection rate RO membrane but is in fact a 90% rejection nano filter.
The other manufacturers 100 GPD membranes are basically the same as a Dow Filmtec 75 GPD RO membrane. Dow says 75 GPD at 50 psi, 90 GPD at 60 psi and 100 GPD at 65 psi. GE and Applied say 100 GPD at 65 psi so it would be 75 GPD at 50 psi just like Dow.

[rbursek]

Atvdave,
I did that, and my 2 300 watt heaterscould not keep up. Besides being very ineficient way yo heat the water.

[mash2k]

Check to make sure that you don't have the RO membrane or any of the filters, etc in backward. That will cause the problem you have....

Don't ask me why I know that...:)