I grow grapes.

To enlarge my small vineyard I root grape cuttings in January and Febreuary in my basement...I live in Wisconsin's Zone 4, and it gets as cold here as the Twin Cities in MN just across the river from me.

To speed up the rooting I have to get extra heat to the rooting area of the clipping. Small electric heat mats are out...and expensive...I'll root about 250 cuttings this year.

'Ive designed a table, 4' X 4', and 8 inches deep.It has a bottom. My plan is to use either copper tubing or PVC tubing laid inside on the bottom and covered with rooting medium. The tubing will be connected to a small domestic water heater dedicated to this project alone, a thermostat, and circulating pump to circulate the hot water through the tubing which (will transmit the appropriate heat to the root area of the cuttings).

NOTE: Rooting medium (such as a combination of light weight potting soil) will be poured into the table compartment up to about 7 inches, and the cuttings placed deep in the medium to about 1 inch from the bottom.

I want to keep this simple..and inexpensive...i.e. no expensive gadgets and controls...what I'd call a "Rube Gpldberg"...a term used in my day to define a very simple setup.

So...what size or type pump (perhaps being used for some similar duty) would you suggest?

Next, since this would be a closed system which simply circulates hot water from the heater to the table and back to the hot water heater tank, ...will there be any poressure concerns?

And...any other suggestions or critiques?

THNX