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I see a lot of talk about storing rain for later use in a greenhouse... But what about letting the rain flow into the greenhouse instead of storing it?

If a small 6'x9' greenhouse has gutters, would there be more harm than good if the gutters somehow diverted water inside? I'm thinking of a pipe or hose that directs water from the gutters and brings it inside and then uses a soak/drip irrigation hose to administer it to the plants.

Greenhouse gutter diagram

Bort
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One of the cool features of greenhouses is that you have more control. Storing water makes more sense rather than hit or miss by rain...to include over watering. Our gardens are always going to be artificial. We humans will always be completely responsible for every little thing our plants our crops need to survive.

If you want to be successful with plants you have to be on call every day, watching, asking questions. You wouldn't know how much water your plants have gotten leaving it up to a non automatic automatic system.

Try as we might there are no easier, better and easier ways to grow plants than the basics. The basics are straight forward, tested and work. Water deeply then do not water again until the plants start having trouble pulling the water out of the soil. Do not water just to be watering.

It is akin to remaking the wheel.

stormy
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Two things: Most rainwater collection systems have a diverter to allow the first few minutes of rain to NOT go into the collection barrel, or what have you. This first water tends to have a lot of dirt and dust in it. If you created a system like you describe, you may want to rig up some sort of diverter to avoid this water.

The other thing I thought of was the water pressure. Coming from the roof/gutter to a bench or floor may have more pressure than you need. If you do manage to deal with the pressure using soaker hose you may run into the water backing up into the gutter and spilling down the side of your greenhouse.

Rainwater is definitely better than tap water, IMO, but it does lose it's acidity sitting in a barrel, so there's that.

Tim Nevins
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  • I'll have to look into the diverter. If water backs up at the gutter, then it would just be how it is already (water runs off the end). – Bort Apr 02 '18 at 20:31
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    How does rainwater lose its acidity sitting in a barrel? Don't think pressure coming off a roof is even noticeable. Rainwater is tons better than tap water tell everyone why, please. – stormy Apr 02 '18 at 20:35
  • Gathering air borne contaminates acidifies the water. Sitting will lose some of the CO2? – Graham Chiu Apr 02 '18 at 20:52
  • CO2 is not an airborne contaminate. Heavy metals are. – stormy Apr 02 '18 at 21:17
  • SO2 and NO acidify rain water along with CO2. Not sure why acidity would be lost either unless it's being neutralised by all the bugs falling into it! – Graham Chiu Apr 03 '18 at 06:01
  • CO2 will come out of solution if the partial pressure of CO2 in the atmosphere is reduced, however, I can't image that there is likely to be a significant difference. The effect of SO2 and NO is much more permanent so I can't see how that would change on standing. – George of all trades Apr 03 '18 at 07:37
  • The advantage of rainwater is really going to depend on what you are growing and where you are: one of the main reasons for using it is that it will have a lower pH than groundwater in a 'hard' water area and so is better for water calcifuges (lime-hating) plants. – George of all trades Apr 03 '18 at 07:42
  • It won't be treated which means that sodium hypochlorite (some parts of the world still use chlorine, but most treatment plants don't because it's a lot easier to get wrong) and sodium fluoride (if your local water supply is fluorinated) will not be present. This means that there will be fewer sodium ions and fewer halide ions present. This can be beneficial for particularly sensitive plants. Of course if you live anywhere near the sea then the effects of salt spray will completely eliminate any such advantage – George of all trades Apr 03 '18 at 07:43
  • George of all trades let's talk about fluoride. It is not sodium fluoride, right? It is Hydrofluorosilicic acid PLUS...right? How tough is it to distill water and will that get rid of hydrofluorosilicic acid, sodium hypochlorite? How much buffering does decomposed organic matter do for soil pH? – stormy Apr 03 '18 at 23:24