Question: Hot water germ table

I'm going to post this here as well as in the HandyMan Forum hoping for some input.
I recently put a water heater in the greenhouse. (My well water comes out of the ground at 55* and really hurts my seedlings as well as slowing down germination.) Altho I have electric heat mats to germ many flats on I still run out of room (they only hold about 25 flats). So....this is what I'm thinking:
Since many bigger greenhouses (as well as residences) have hot water pipes imbedded in their floors to provide heat it seems like I could lay out garden hoses in a zigzag-type pattern on a large table, run hot water thru them and set many many flats directly on them. In order for the water to stay hot it will have to be constantly moving thru the hoses so I was thinking of a return line going back into the cold water inlet side of the water heater. However, it would seem to me that the main water IN line could work against the returning 'cooled hot water' and block that water from entering the water heater. So, then I thought of putting a cut-off on the main water IN line but(!) that means that no water entering the water heater also means no hot water is being pushed out. There must be some way to have the IN line putting water in the heater (but not putting it into the hot hoses) and have hot water circulating thru the hoses, then as it cools returns to the water tank.
Any ideas? Confused yet? Know of any plans or websites that would address this issue?

I posted in the Handydandy Shoe,lol'

Horseshoe....many homes are now putting in their own water supply reseviors...surely there are some websites on water conservation and retention tanks that may offer you some fodder for thought...

"eyes"

..G.A.T. Technology, Ltd....

"eyes"

Shoe fill every thing up and then get a pump on the hot water side and go back into the cold with the return line you may have to shut off the well water line but won't have any trouble with hot water heater as long as the heater is full of water hope this helps you could lay the the table with copper or plastic and would still work fill in between with sand and will give even heat put a coil in the wood stove that works fine too
good luck

Great suggestin dave...any idea how big a pump I'd need? Think a small sump pump would work? (seems like it would to me, if it could handle the hot/warm water...I'm only gonna heat the water to about 70*).
Eyes, will check out GAT first thing in the morning (I'm getting weary-eyed.)
Thanks folks. will let ya know how it goes.

Shoe I can't remenber what the volume on a swamp cooler pump is that size works a lot would depend on how large of table you make if it is 60 ft you will need to be larger 60 ft' 4 line 1/2 od pipe figure amount of water and change it every 3 min or so so 60X4 =120 feet how much volume of water take cup water and measure 10 lenght would probley be the easiest to get a close figure thinking out load here
was figuring a 2X60' table for zone 5/6 line that is why the 4 lines you may not need as much warming were still dealing with 20* nights we hope it doesn't get colder the record yesterday was 22 below

Well, we're having some sporadic nites in the 20's also, however I don't let that part of the g-house get below 50* (usually...maybe a corner here or there may get to 40-something).
I used to have a pump that was used for a swamp cooler...I ended up using it to pump water out of my rain barrel..if it wasn't hooked up to a hose and just pumped water it would shoot the water a good 25 feet or more!
By the way, another thought I was thinking...I see second-hand water tanks from time to time...what if I hooked a second "holding tank" to this system? I could run the hot water line from the water heater into the holding tank, run my hot "germinating line" from it and return the cooled 'hot' water to the holding tank. Seems like this would keep the main coldwater IN line from being compromised. Does it sound like that would work? (I realize that the cooled hot water might reduce the temp of the "real" hot water in the holding tank but perhaps it wouldn't have a big affect.)
Any input on that?

Shoe, my friend Dianna uses a "Finn" system to heat her tables. I will see what I can find out from her. I know it has a boiler and a pump, but not sure how it works. I think it has a resevoir too.

Shoe set your tank over the wood stove and it would work find

I wish...the wood stove is in my "shoffice", not in the greenhouse. I do have a superbig gas heater in the greenhouse (suspended in air) but putting anything holding water on top of it might be a bit heavy for it.
Dave...I think you'd like this system too! I can just tell you're enjoying this thread!

'Shoe, great minds think alike. I'm doing the very same thing! Kenny's already built the table and we're just waiting on the time to install the water heater and hook it up.

This will be the order we install the stuff ~ cold-line-in, then cut off valve, then a T that goes to the heater intake and also past it to an in-line pump and into the table. We'll do the same thing on the other end. I'll keep the valves shut until I need to use the hot water in other parts of the greenhouse. I'll probably turn the table pump off during that time.

I had thought of using a jacuzzi pump, the water being hot and all, but when I priced them ~ YEEEOOOWWCH! I found a sump pump that had male and female hose ends on it for 60 bucks at Home Depot. But then Kenny thought this old RV he has in his playground just might have a water pump in it. Sure 'nuff, a perfect in-line pump that runs off of 110 current! I hope it still works. And to think I gave him 9 kinds of grief when he drug that butt-ugly thing in here! Of course, it was raining at the time and his playground road was all muddy, so he had to park the thing right in front of my garden 'til the road dried out. And is it ever ugly! UGH! We've made a deal ~ he's gonna' top the road to his playground and I'm gonna' let loose of the money for the chat without complaining. ;-)

BTW, the table is just a plywood one, with holes drilled in the plywood and a 2x4 band around the edges, making it a trough. We lined it with window screen from old windows we've had around, filled it with a couple inches of sand and snaked 1/2" cpvc through it.

Just reading through my description above it's kind of hard to follow. I'll draw a diagram of the pipe hookups in my Paint program and see if I can't post it somewhere on these forums. I'll take a picture of our table, too.

This message was edited Saturday, Feb 16th 2:42 PM

Here's the plumbing diagram. http://www.moment.net/~wingnut/images/germ_table_plumbing_diagram.gif
And here's the pics of the table. http://davesgarden.com/editgj/viewentry.php?rid=11953

Great! Yep, sounds like you better post a pic...my mind works well with pictures! You're putting a T on the inline (cold water) and over to the hot water line? Sheesh, my brain is fried from thinking about this stuff! I'd love a pic.

We musta' been posting at the same time, 'Shoe! LOL! Yeah, when I first read that again, it made the intake line on my brain cross over and get backed up with the outgo, then cross to the output, then tied in to the backflow. What a mess. Makes my brain hurt. Pictures ~ MUCH better.

Hah!!! You ain't right girl!!!
Okay, gonna go check out your links...thanks!

shoe the last one i made had a barrel stove with the heater coil runing around the out side glad he remimed me about rv water pumps i thin i still have one if it is still good hope you both have great luck with your projects

dave...someone was here today telling me how they made a water heater when they were in boy scouts...a tank of water, a coil that was over a fire, and the coiled line circled back to the water tank. The fire under the coil would heat the water in the coil and it kept a constant hot water in the tank...great idea. Thats what I thought this project was gonna be, or something similar. (and it still may be that!).
Am still checking it all out. Got a good lead today. Will post more when I follow it up.