Re: Jim Kelly's vermiculite recipe

In message "Re: Jim Kelly's vermiculite recipe", Steve Pushak writes:

>Yes, that is a good point. My plan is not to use a powerhead of any sort but
>rather only about 1-5 cm of hydrostatic pressure. I hope that will be sufficient
>to induce a suitably low flow rate as per the heating coil method. I think I
>should be able to alter the hydrostatic pressure by the height of a tube which
>receives the outflow from a filter or pump. (drill holes whatever) I will post
>this on the list and hope for additional comments. Does anyone have any idea
>of how much hydrostatic pressure would be ideal or the ideal velocity of water
>being transported through the substrate or a method for measuring this? The
>flow rate should be dependent only upon hydrostatic pressure differential, the
>thickness of the substrate and it's liquid permeability. Sounds like data we
>should be able to discover from soil lab research.

I don't know whether a 5 cm head of water will be enough to provide
adequate circulation, and I don't know what the ideal rate of
circulation is, either :-(.  I do have a suggestion for determining
the total rate of flow.  You drip water into the intake at a constant
rate.  And wait till the level water stabilizes.  Then measure the
height of the water column and the rate of inflow of water.  You could
create a nice graph showing the variation of flow rate with water
column height.

>Is everyone still getting the mailing list except me? The last one I
>got was 108.

Works like a charm for me, and nobody else has complained.  I am also
getting regular email from the server promising me that everything is
under control.  I'll try unsubscribibg and resubscribing you.

Shaji Bhaskar                                              bhaskar at bnr_ca
BNR, 35 Davis Dr., RTP, NC 27709, USA                      (919) 991 7125