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Discuss water requirements, "soil" (growing media) and suitable planting containers

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By MikeB
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Posts:  1253
Joined:  Sat Apr 25, 2020 4:13 pm
#409333
I'm thinking about getting an RO unit as an emergency water supply. I prefer to use rainwater since it's free, but for any long stretches when it doesn't rain, a decent RO unit is preferable to hauling gallons of distilled water from the store (especially when I burn through 20 gallons every other day). My biggest complaint about RO units is the amount of waste water, but I found a high-efficiency model that looks promising:

Waterdrop Reverse Osmosis Water Filtration System, Tankless, 400 GPD Fast Flow, 1:1 Pure to Drain, model WD-G2-W
$299.99
https://www.amazon.com/dp/B082CZ9XZ9

1 gallon of waste water per 1 gallon of RO - much better than most other units. I'm planning to get a booster pump to kick my water pressure up to 80 psi. If it really does 400 gallons per day, that amounts to 16.67 gallons per hour (or run for an hour and fifteen minutes every other day to make enough water for my plant collection). I can have it dump the RO water into a 5-gallon bucket, then haul it outside and pour it into a rain barrel. My tap water runs 120-150 PPM, so the filter won't have to work very hard to bring the mineral level down.

For another $60, I could upgrade to this model:

Waterdrop RO Reverse Osmosis System, 600 GPD, 2:1 Pure to Drain, Tankless, model WD-G2P600-W
$359.99
https://www.amazon.com/dp/B08746M1NX

It's rated at 600 gallons per day and makes just 1 gallon of waste water per 2 gallons of RO.

This looks very promising. Does anyone have any experience with this brand?
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By specialkayme
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Posts:  226
Joined:  Tue Apr 13, 2021 11:02 am
#409354
Why are you looking at tankless systems? Just curious.
MikeB wrote: Wed Apr 27, 2022 1:40 am If it really does 400 gallons per day, that amounts to 16.67 gallons per hour (or run for an hour and fiften minutes every other day to make enough water for my plant collection).
My understanding with most of the RO systems that are on the market is they require pressure to maintain a low TDS. Tank systems maintain the pressure internally, so you turn the faucet and 2 ppm TDS water comes out of the spigot. Done. The systems you link to require an internal pump to force pressure into the system. That means the first glass you get will have a TDS reading roughly equivalent to your tap water. Then after 30-60 seconds the filtration starts kicking in as the pressure builds up. That means you'll have the waste water from that constant running that isn't counted in the 1:1 or 2:1 calculations.

May not matter for your application (filling a 5 gal bucket up). But produces considerable excess waste water for a glass, pint, or quart at a time. The extra run time will wear on filters faster, and the added moving parts will add on wear.

I don't have any experience with this system , but 400 gallons per day seems incredibly high for a under the sink system. The average US household uses 300 gallons per day for all applications (including the high water uses of washing machine, dishwasher, and showering). I know I use about 2-3 gallons of RO water a day (for personal drinking, coffee machine, and plants). Seems suspicious to me.
MikeB wrote: Wed Apr 27, 2022 1:40 am I can have it dump the RO water into a 5-gallon bucket, then haul it outside and pour it into a rain barrel.
Why not just run the waste water pipe directly into the rain barrel? No 5 gallon buckets to haul.

But in that instance I guess the question is whether you'll use all the waste water (whether 1:1, 2:1 or 4:1). If so, it isn't really "waste" water.

Just some thoughts though.
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By MikeB
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Posts:  1253
Joined:  Sat Apr 25, 2020 4:13 pm
#409432
specialkayme wrote: Wed Apr 27, 2022 1:46 pm Why are you looking at tankless systems? Just curious.
Three reasons:
  1. I have two 60-gallon rain barrels. If they're empty, then I have plenty of water storage space.
  2. I require 20 gallons to do a full watering of my plants. A tank with that capacity would eat a lot of space inside the house (particularly under the sink).
  3. If I use a tank, I'll still have to empty it into a rain barrel so I can make the next batch. I might as well use a container that's designed to be moved.
specialkayme wrote: My understanding with most of the RO systems that are on the market is they require pressure to maintain a low TDS.
I'm also looking at a booster pump to do 70-80 psi on the incoming feed.
specialkayme wrote: May not matter for your application (filling a 5 gal bucket up). But produces considerable excess waste water for a glass, pint, or quart at a time. The extra run time will wear on filters faster, and the added moving parts will add on wear.
I'm planning to make at least 60 gallons per run, enough to fill one rain barrel.
specialkayme wrote: I don't have any experience with this system , but 400 gallons per day seems incredibly high for a under the sink system. [snip] Seems suspicious to me.
Yeah, that number seems pretty high to me, even more so for the 2nd unit at 600 gallons per day. The company does have a 30-day return policy:
We accept return reasons including defective, no longer needed, change mind, not as described, etc.
Producing substantially less water than advertised falls under the heading of "not as described" in my book.
specialkayme wrote: Why not just run the waste water pipe directly into the rain barrel? No 5 gallon buckets to haul.
If you mean the RO water, then I'll need a longer hose. The RO unit will be indoors, at least 30 feet away from the barrels.
specialkayme wrote: But in that instance I guess the question is whether you'll use all the waste water (whether 1:1, 2:1 or 4:1). If so, it isn't really "waste" water.
The less leftover water that it makes per gallon of RO, the better. I'm looking at ideas about how to use the waste water instead of just dumping it down the drain. Maybe I'll pour it on the yard; if I'm in the middle of a drought, the grass would appreciate it.

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