GH water improvements

I have a supply of well water to my greenhouse. This water is not suitable for long-term use on plants because of the hardness. This water eventually leaves calcium deposits that are unsightly and harmful to the plants.

For some time, I used an RO system with a booster pump. The system charged a large (deep well) bladder tank and stored about 15-18 gallons of water total. This type of system has its flaws, namely that the booster pump wears out (twice in 3 years) due to the high back pressure on the system and the fact that it is running all the time. The system goes through lots of membranes, which are expensive. It doesn't hold much water. And finally it doesn't take advantage of free, clean water in the form of rain. So I reengineered the entire system. Thanks to tigerlily123 for the original inspiration, and thanks to nautical99 for sharing the details of his system with me.

First I attached gutters to both sides of the greenhouse.

This message was edited Aug 3, 2007 3:05 PM

I removed a pane of glass and replaced with Lexan, then I ran 2" pipe around and through the Lexan and into the GH. I wrapped the pipe around the corner so that I did not have to see the greenish Lexan from the house.

I set up three 44 gallon barrels inside. One is under the potting bench. I will build another bench on top of the other two.

I ran the raingutter "downspouts" into the two barrels on the ends. I didn't want cold water in the winter displacing the warm water already in the barrels. So I switched the 2" schedule 40 PVC to a flexible pipe that I can remove from the barrels and drain onto the ground in the winter if needed. Underneath my greenhouse floor I have a system of 4" perforated drains which will run the excess water about 20' downhill from the GH.

The barrels are all connected, and each barrels has its own shut off valve. There is a shut off valve for the entire water supply, then there is a filter, then a check valve...

I need to get that filter off the ground, or else I'm going to step on it and break it. Anyway...

When the rainwater supply is inadequate, the RO system makes the water. It knows when to kick in based on float sensors in one of the barrels. The sensors are lower on the barrel than they would otherwise be, because I wanted to maintain the capacity to accept rainwater into the system. Otherwise, the system would fill with RO water and the rainwater would just overflow.

The float sensors control a 24VAC solenoid valve which in turn controls the water supply to the RO system. There is also the capacity to add a booster pump, but so far I seem to be making enough water without a booster pump. Here is the solenoid valve and the RO membranes.

The line from the barrels runs to a pump. This is a demand/delivery pump which charges a ~20 gallon bladder tank. I precharged the tank to 40 psi, and the pump cuts off at 60 psi. The tank holds 6 or 7 gallons of water at these pressures. The tank recharges so fast that I can water the whole greenhouse without interruption, and the water pressure is excellent. The overhead mister make a nice foggy mist.

This message was edited Aug 3, 2007 3:22 PM

Now if it would just rain...I believe that I will be able to supply the GH with rainwater for most of the year. The RO system should run only during the summer.

I think that this system is more reliable, less expensive, and more eco-friendly than my old system.

I hope that this is helpful to someone thinking about their own GH and it's water supply.

Thanks man! That's a sweet system (heck, it was before!). =)

You know you're making me REALLY wish I got a bigger GH, don't you? =P

Great post!
I love my system, it works well and so far have have always had plenty of "good" water for the plants. When I started this project 6 months ago I had no idea that my "clean" city water was not going to be good enough for the plants.

I think it was DD that first made me aware of the problems with city water. And of course from all the other members that post here and share their knowledge, I can't imagine how frustrated I would be about now, trying to figure all this out on my own.

Ditto Eggs, on wanting a bigger gh. I am a rank newbie at this, but am already wishing I had a bigger gh. I did not want to use up my gh space for my storage tank, so I have my water storage outside, I will have to figure out a way to keep it from freezing in the winter. I don't think it will take much, I am thinking of using a large aquraium heater and maybe insulate the tanks some. The bladder tank is inside the gh so is always warm.

SB, I also have a 20 gal bladder tank, but was told that when pressurized it would hold appox. 14 gal. Did you measure the capacity, 7 seems kind of low to me.

Nautical

Hey again, Skip!

The capacity of the tank depends on the pressure with which you precharge the tank.

This morning I was doing some reading on this, trying to figure out what to do, and up came Boyle's Law, a distant memory from physics class...this helped me figure it out. It has to do with the relationship between pressure and volume for gases: at a constant temperature, P1*V1=P2*V2. So with the tank empty, the gas volume is 20 gallons. I pressurized to 40 psi. 40 psi * 20 gal = 800. Now the pump cuts off at 60 psi. Sorry if I sound like a math teacher...40 psi x 20 gal = 60 psi * X. Solving for "X" gives me 13.33 gal. So the original 20 gal of air now occupies 13.3 gallons, leaving 20-13.33 = 6.67 gallons for the water.

By pressurizing to only 18 psi, you can get 14 gallons in the tank... 20 gal * 18 psi = 360 = 6 gal * 60 psi. The original 20 gal of air now is reduced to 6 gal at 60 psi, leaving 14 gal for the water. Here, though, it would seem that you might lose pressure near the end of your tank, unless your demand pump kicked in and made up the difference. Also, the label on my tank seems to suggest ranges of 20 psi (ie, 20-40 psi, 40-60 psi, etc) and so since the pump cutoff was 60psi, I went with 40. Also, I once had the bladder rupture on a small tank, and I thought that by keeping the charge pressure a little higher, I might protect the bladder a little bit. Not sure if that is really true or not, but sounded good intuitively. ;-)

Now the other interesting thing, and one thing I had forgotten until this morning, is that there is a temperature factor in the equation above, the combined gas law, and it can be restated as P1*V1/T1 = P2*V2/T2. So in the winter, when the GH temp is 55F, my empty tank pressure has dropped from 40 psi down to 24.4 psi. So maybe we need to make pressure adjustments as the weather cools.

Anyway, long answer to your question, hope it made sense.

That looks really nice SB! That was a big job. A few questions....

Where did you get your filter? I have the same one and I can't find it at HD anymore, and I like having a backup (actually I need a new washer and they are hard to find by themselves)

You have one of the barrels apart from the others-is it still connected to the other two with a tube?

When it rains and drains into the two barrels, if they fill up, will the excess go into the 3rd barrel?

How did you keep the holes that you made for the tubing at the bottom of the barrels from leaking water? Make the hole smaller and shove the fitting in? And then what? On my misting system, I had to drill 3/8's holes and then had a rubber thing with threads on one end that you shove into the hole and can then thread the mister head into and that does a good job of preventing leaking.



Nautical-my tanks are outside too, but I usually don't need them in the winter. Unlike you guys, my rainwater is strictly for backup as my well water is fine to use. I have to drain all the water from the pipes from the tank to the filter and then to the bladder tank before we get freezing temps or else the PVC pipes/filter will crack (and the bladder tank). When I start to use it again in late Feb/March I have to drain the pipes and unscrew the filter every evening that we are getting freezing temps. Fortunately at that time of year, its not too many nights, but for you it might be different. Can you insulate all the pipes as well as the tanks?

Hi TL,

The filter came with a misting system kit I bought from Hummert. It looks like that model has been replaced in their misting kit with this one: http://www.hummert.com/catalog.asp?P=11612

For the fittings, I just made a hole in the barrel with a drill and inserted a threaded fitting with a rubber washer. Then I put a nut on the inside.

All of the barrels are connected at the base so the water levels equalize. There is a 1" PVC overflow pipe on one of the barrels in case they get full. I didn't get a pic of that.

You are lucky that your well water is suitable. Mine is nasty.

SB, I got lost when you solved for X. Sorry I did not take math, so could you explain how you arrived at 13.33 number?

I think that is what is happening on my system, the demand pump kicks in and makes up the difference. I am going to empty the tank today, and start over.

If the pressure change was a problem we could fill it with nitogen, which is not affected by temperature changes. There are many places that have nitrogen available now. The trick is to get as close to 100% nitrogen as you can. If you are filling a bladder tank that is empty, with pure N, it should not be a problem. But if the tank you transport it in is not 100% N you can't fill the bladder tank with pure N.

I have seen many tire facilities now advertising they are filling tires with N. I have not seen ANY yet that actually attempt to get close to 100%. They seat the bead with shop air, then finish inflating with N. I don't know the ratio, but I am betting no better than 66% N. The tires need to be filled with N, then defated, then refilled again with N. That would get them a lot closer to the benefit of not haveing to worry about underinflated tires during the cold months. In my opinion, it is a lot of hype with very little substance. (At least in the way it is being used.)

Stepping down from soap box now.......

If you wanted to fill your bladder tank with N you could take it directly to the source. If it was empty you would be filling with pure N and not diluting it with air in the tank. (Providing the equipment they are using is functioning properly) Or if you have a portable air tank that you want to use, you could fill it with N, then purge all the air out, then fill it again. That would be close to pure N.

Anyway now I have some more to think about. Thanks for the post.

Nautical

Skip,

So you are replacing your tank? Post some pics, please, you are welcome to post here if you want. I can tell a noticable bump in pressure from my watering wand when the pump kicks on. So it sounds like it may not matter too much what the tank is charged to, as soon as the pressure drops, the pump kicks on regardless.

Using P1*V1=P2*V2, 40psi*20gal = 800 = 60psi*13.33gal. So the original 20gal at 40 psi is compressed at 60psi to 13gal. At 80psi it would be 10 gal, at 160psi it would be 5gal, and so on.

Interesting about the nitrogen. Short of removing the fittings on the bottom, I don't know how you would replace the air with nitrogen. You could repeatedly pressurize, release, and refill, the way you have described, and that would give you expontentially less air each time, but it wouldn't reach 100% pure nitrogen. For me it is probably easier to drag the compressor out to the GH and add a little air. ;-)

SB, How are you charging your tank with air now? I am assuming you have a shrader type valve at the end of the tank, just like a tire fill valve. That is where you would add nitrogen if you wanted to do that. I agree that it is probably not worth the effort.

I am going to replace my outside storage tank. I used a heavy duty trash bin, but it was not strong enough to hold water. When it filled, it pushed out in the front. It is holding water ok, not leaking anywhere, I just am not likeing it. It is mis-shapen, (is that a word?) now and where my bulk head fitting is located at the bottom of the tank, it is on a bad angle.

TL, Yes I plan on insulating the pipes for winter. Another thought would be to set up a cycle timer and just move a little water during the cold nights. Would still have to protect the RO supply tube though. It does not get real cold here often, but certainly enough to freeze pipes, so I will have to work this out before winter.

Are you guys saying that the pump should stay on (or off) all the time that you are watering? Like what SB said-mine kicks on and off every 5 mins or so when we are watering and the pressure of the water falls and then increases after the pump kicks on....is it not supposed to do that? I know that you can adjust it some, but does it really matter?


Nautical-why can't you take a strip of metal and tighten it around the trash bin in two places -near the top and one third of the way down, so it doesn't bulge out? You know the rolls of metal strips that are about 1" wide with holes cut in them every inch or so?

TL, my pump does just what yours does, I think that is how it is supposed to work.

Nautical, my tank has the fitting you describe, it looks just like the one on a tire, and I just fill it using a compressor.

"I love my system, it works well and so far have have always had plenty of "good" water for the plants."

Right.

I posted that last night at about 10:30 pm. I was in the gh this am, putzing around and all was well. I decided to fertilize all the outside flower beds today, so busied myself doing that.

At about 3:30 this afternoon I went back out to the gh with a spade bit, electric drill and a piece of dowel rod. My purpose was to bore a hole and put the rod in and have a place to hang a roll of paper towel. The gh seemed unusually hot and dry. I first noticed that there was no sign that the misters had run. I started looking around and did not see any sign the plants had been watered either. So I picked up my watering wand and........you guessed it, no water.

A quick check revealed the booster pump had quit running. Checked breaker, water supply etc, all good. I found that the internal pressure switch had failed. I should never have bragged that it was all working so well......

I by-passed the pressure switch and wired in an old fashioned well pump switch. Works great, have not checked the cut-out pressure yet, but I think it is close to 60 psi. It is adjustable if not where it needs to be.

I am so glad this failed now, and not in two weeks as I will be out of town for awhile and the person that is going to watch over things would not have been able to sort this out. I also realized that the big flaw in my system was that when I put in the RO system, I totally isolated it from any other water source. Big mistake. Tomorrow I will plumb in a couple of tee's and a ball valve so that if the RO system goes down, city water can be used until repairs are made.

TL, I could strap the tank as you suggested, but I am just not liking the tank. What I did not add earlier was that it leaked about half way up where the factory had molded a grab handle. I had to drain the tank, cut the handle out and silicone the pockets in. It is not leaking at all now, but I wonder what it will do when we see some cooler temps.

Anyway I have re-assessed the situation and like SB's setup and will most likely put tanks inside and not have to worry about freezing issues.

Also, my pressure remains almost constant, and the pump cycles on every 2-3 minutes if I am watering with the wand, less if the misters are running.

I checked the pressure on the tank, with the pump satisfied and it read 45 psi. Maybe I should shut down, drain all pressure and re-check it.

here are some water tanks of various sizes and shapes-I have two that are 2100 gallons each and they are very sturdy, but they have much smaller ones as well that could go under benches etc. I know what you mean about the trash bins and what they can do when filled to the top with water, these seem a better long term choice.


All this talk of water....and we are in a serious drought! No chance of rain for at least a week and temps going to hit the high 90's

edited to include the website of the tanks http://www.tank-depot.com/browse.aspx?id=2

This message was edited Aug 4, 2007 10:20 PM