most mixes straight from the shop will bottom wick, as they contain largely peat, which wicks easily. but if you let it sit too much - it might absorb too much water. peat needs to be cut with perlite roughly by 25-30% , so as not to get water-logged. if the mix is coir peat however, it will not get water-logged, even though coir-peat actually absorbs a little more water then reg peat. but it maintains air-spaces even when wet - so the roots can still have air. IF your mix contains coarser coir pellets (chips) - they maintain as much air-space if not more then bark. they wick up very well too, but bark does not wick. so if your mix contains mostly bark (more then 50%) - it will wick some but poorly, only the bottom layer (which is usually the wettest anyway). for bottom-wicking in general the 1:1:1 ratio of bark/peat/perlite is recommended (see raybo mixes for example).

Here's a link to several of the previous discussions of this question. You'll find all the details there. Just scroll down to the ones with the blue borders. Dave Here is a link that might be useful: Bottom watering how-to

z, I don't believe there is any general rule for this sort of thing. You may ask this question in various forums where these types of concerns are common like the Container, Vegetable, Flower and anything grown from seed forums. The only thing I know about this sort of thing is one) the water behaves different in different types of soil Clayey versus Sandy) and 2)that watering from the bottom may dislodge the seed and may damage very tender roots from seedlings. I do use wicking from the bottom into containers via roping in tomatoe container gardening. GL Aloha

I guess i don't understand the point of the secondary drain. I've seen when drains clog with mold, but that's only after many years.... so I don't know what the secondary drain would accomplish here. A malfunctioning TXV could cause it to ice, as well as low charge and restricted airflow... but usually you see that in a cap tube system since the TXV is regulating the flow into the evaporator based on evaporator temp. I understand that it produces a lot of water, but you have a cutoff system in place. A secondary water barrier should prevent water damage as long as the cutoff is working. It's not so much that the volume of ice is too big to be contained by the pan... it's that it extends beyond the pan to the suction line and the possibly the coil housing. If it were iced up like that, you should be getting almost no airflow through the unit. "The tech who came yesterday did check the charge and said there was good pressure (but he also recharged it)." ... those things are mutually exclusive. You don't add refrigerant to a unit that is properly charged. What's more, you don't guess at the charge and you can't properly charge a unit where the TXV has failed because sub-cooling is the the only acceptable way to determine the proper charge. Look, if it's icing, you really need to see that. You can't guess unless you see why the unit is leaking... you have already done that and you've had to repaint the ceiling a couple of times.