Self Watering Container Reservoir Idea

ehsteveJanuary 19, 2014


I have been trying to grow peppers and tomatoes in self watering containers and top-watered containers for the last two summers, and have slowly improved my growing success but have found it very difficult to keep the plants sufficiently watered if I'm away for more than a day or so.

For the SWC I use Raybo's 3:2:1 and for the top watered I use Al's 5:1:1. both in ~7 Gallon containers. The reservoir in the SWC holds about a gallon.

The issue is the plants are on a rooftop terrace where they get full sun for almost the entire day and it gets very hot in midsummer, causing the plants to burn through their reservoirs very quickly. If I'm away for the weekend I can expect to come back and find them all wilted, which can't be good for their productivity.

So I have a plan and wanted to check if anyone here had tried something similar first...

This summer I plan to construct reservoirs out of timber, with a polyethylene lining, punch holes in the pots (they're fiberglass or plastic) and out the pots in the reservoir. I plan to put a lid on top to help control evaporation, prevent algae bloom and discourage mosquitoes.

The containers will be 6 feet long by 1 foot wide by 6 inches deep (made out of 2x6 timbers) and each will have three pots in it. With a water depth of 3 inches the reservoir will be about 11 gallons, so about 3.5 gallons per plant. If I go to 4 inches water then the reservoir will hold about 15 gallons, or 5 per plant. Which should be plenty to keep the plants watered even if I'm not able to attend to them for a few days.

So... are there any issues with this plan?

Will I have problems with mold / fungus in the reservoir? Or no more than with any other SWC?

Is it OK to just put holes in the pots so water can get into them?

I plan to just have the pots filled with 3:2:1 mix, even in the section that will be submerged most of the time. Is there an issue there?

Would I need to put a ton of fertilizer in the reservoir?

Below is a rough sketch of what I plan, made looking along the reservoir so you only see one pot.

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the bottom 3" of roots will be submerged in water, don't think they will like it.

Why not just buy a timer and put in a microsprayer:
C-Frame, 360ð Micro Sprayers

My potted plants are doing much better since I switched to these.
They don't need to rely on me for regular watering. And they don't have the overwet problems swc's have.

    Bookmark   January 20, 2014 at 1:25AM
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what about earth boxes? have you looked into it?
i've seen a lot of posts here using rubbermaid tubs as water reservoirs.

Here is a link that might be useful: nice SWC setup

    Bookmark   January 20, 2014 at 10:22AM
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Ohiofem(6a Ohio)

If you have the technical skill and money to build such a thing, I think you would be better served to build or buy much bigger self watering containers. An Earthbox holds 15 gallons of potting mix and 3 gallons of water. An Earthtainer holds 30 gallons of mix and 10 gallons of water. A full grown tomato plant uses at least 1 gallon of water a day, according to what I have read. If you buy or set up an automatic watering system, you wouldn't have to worry about watering.

I don't know how your system wicks water. It appears that you plan to set up the pots so the potting mix is in direct contact with the water, which could be a disaster.

Full disclosure: I have never grown in a SIP. I got one for Christmas and have been doing a lot of research on how they work.

    Bookmark   January 20, 2014 at 10:43AM
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Thank you for your responses.

I suppose my goal is to construct something like an earth-trainer but with removable pots.

The terrace is about 40 feet of stairs above the ground level and it'll be rough carrying a 15 gallon container of dry soil up there and then back down come fall.

The pots themselves are about 16 inches tall, so would provide at about a foot of soil above the waterline, from where I intend to wick directly into the pot.

Looking at Earthtrainer the idea (to me) looks similar:

But instead of the whole lower section of the pot being submerged only portions of it dip into the water.

If this is a critical detail then I could basically add in a layer of filter fabric and filler in the base of the pots so that only a section of the container soil dips into the water - would that address the issue of waterlogging somewhat?

    Bookmark   January 20, 2014 at 12:57PM
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yes, only part of soil (soil-well) is critical. it is a wicking well.
if you want to use a filler - it needs to be a wicking filler to deliver water to the roots. you could use leca/hydroton or lechuza aggregate for that. the roots will grow into it over time, but you'll need to top water in the beginning. neither one is cheap.
there are self-watering insets of all kinds that have a well dipping into water - you insert them in your pot with water. you could use another bucket underneath to hold water, then insert - probably needs to be propped up high somehow above water. and then your soil pot.
you need to search for var keywords - there's a lot of posts with diff set-ups in this forum. check also hydroculture and do a google on 'lechuza pots' to see how it works.

    Bookmark   January 20, 2014 at 1:27PM
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Thank you - I didn't realize there would be an issue with having the whole pot submerged to wick compared to just having a limited wick extend into the reservoir.

In my previous iteration of SWC's I used upturned salsa jars (about 4" tall) to support a plywood sheet with a pair of holes cut in to allow the wick down to the water and with a filter fabric to prevent soil loss into the reservoir. I'll see if I can adapt that system to make sure there is an air gap between the growing soil and the high water mark.

    Bookmark   January 20, 2014 at 2:17PM
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i use self watering wicks for a lot of my indoor container grown plants. i use various ready made mixes like 'palm/citrus' or cactus or african violet mixes that contain less peat then regular bagged miracle-grow mix and then i add 40-50% more perlite for wicking. i think you need that much perlite fro it to wick properly, but stay aerated.
i use braided nylon rope for wicks. usually for 12" pot i use 2 wicks. for thirsty tomatoes you might need 4-6 wicks per bucket. the larger the bucket the harder to wick the water up.
why not use bucket in bucket system: drill holes thru the bottom of one, drop wicks thru, fill bottom bucket with water.
the bucket will sit very high up. you can snip an opening in the rim of the bottom one to allow for water refill.

    Bookmark   January 21, 2014 at 10:17AM
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