Can you use a waterbed heater to successfully heat a 12ft x 3 ft deep
round pool?  Pool is an above ground Intex self rising pool.

---

Clarification of Question by abby43-ga on 03 Apr 2004 10:36 PST

More information to consider...
   I am NOT looking for an exact calulated or "scientific"
answer...just general thoughts. I mostly want to know if anyone else
has tried to heat a small pool with a waterbed heater and if the idea
is a workable one. (or am I going to burn down my house??)
   I want the pool temp to be 80 degrees. Pool is 12ft x 3ft high. It
is currently 55 degrees (just added water)outside temp today is 65
degrees.  By this summer it will be 85  and above every day.  Last
summer the water temp stayed at 70-76 degrees and was just a bit too
chilly to swim in. The pool is NOT located in sunlight but on my
covered screened in back porch area.  I do have a plastic cover on the
pool to keep some heat in. I have 9 inches of water in it right now
because the heater manuel said it must have at least 8" of water
before the heater is turned on.  How long should it take to see at
least SOME increase in temperture?

You will need to provide additional information as to the ambient
temperature in the area around the pool, the insulation values of the
sides and any cover over the pool as well as the starting temperature
and desired temperature of the water(this will determine heat loss
from the "system") as well as the power output of the heater - which
will determine heat gained.

If Loss is greater than gain then it won't work.

As heat loss will increase with greater difference between water temp
and ambient temp there will always be a maximum water temp achievable
whatever size of heater you use.

Burning down the house is very low probability, but a minor electric
shock hazzard is possible if the vinyl liner leaks over the pool
heater. Plugging the heater into a ground fault outlet such as many
bathrooms have should reduce the shock probability to near zero.
 My guess is one waterbed heater will produce a 1/2 degree c = 0.9
degrees F temperature rise in about 10 hours in a pool that size. Heat
loss will prevent that temperature rise from doubling until the
ambient temperature rises. I think you will be disappointed in the
results.   Neil

Great Minds think alike!!
I asked some water bed manufacturers about this last year. The
technical experts stated that the biggest concern would be what they
called "bottoming out" If the person stood on the heater (while it was
on) there was concern that it could burn though the bottom of the
pool.

I am going to try a water bed heater this year. If any one sees
particular concerns please post to this discussion.
1. I'm placing plastic on the ground.
2. Plywood on top of the plastic.
3. The water bed heater on top of the plywood.
4. The pool on top of heater.
5. The electronic controller will be placed in a water tight storage.
6. I'm installing a time controlled switch for the power so the
water bed heater will only be on during the night.
7. As an additional preccaution I'll unplug the heater when the kids are in it.

Finally there are a variety of insulated pool covers that prevent heat
loss when the pool is not in use. Some are dark and use the sun to add
additional heat to the pool. It sounds like you may not benifit from a
solar blanket but any type of thermal pool blanket really helps to
retain water heat during chilly evenings..

PS 
last year I rigged a portable heater to heat the pool. It was a simple
ambient oil type heater that would get warm to the touch but never hot
enough to melt plastic. I then extended the output pool filter hose so
it would wrap around the oil heater about 5 times. The whole rig was
contained inside rain resistant cabinet. It worked pretty well but
seemed less efficient than a water bed heater.

The year before I rigged a automtive tank heater (They are used to
keep the automobile antifreeze warm during cold winter nights). I
hooked it to the pools water filter output hose. That solution worked
great and was pretty energy efficient but the tank heater began to
rust by the end of the season and turned the pool to an amber
color--Yuck!

Hope this helps.
If anyone has other ideas please post!
Brad

THANK YOU BRAD!
   You have been working at heating pools much longer than I it
appears!  I am glad you spoke to someone who makes the waterbed
heaters...  That makes me feel better.  I have my "experiment" set up
and ready to try...but I want to be home when I turn the heater on, so
I can turn it off quickly if necessary. This is how I "layered" my
pool heater.
   1.  plastic on the carpeted floor. (outdoor type carpet)
   2.  double thickness of a polyester fabric. (Polyester is flame retardent)
   3.  Heater
   4.  another layer of polyester fabric...(not sure if I should have done
                                            this or not...and of course I 
                                            can't get it out without dumping
                                            the pool water.)
   5.  Then the vinyl pool bottom on top of that.

 
    When I actually turn it on and test it...I will re-post what happens.
    ANYONE who can add a thought on this subject...please please POST!!
     Abby43

I would like to know how its going!  I remember the old science
project where if you took a cup of water the cup wouldnt burn until
the water was all boiled out.  Its something to do with energy being
transfered to the water than burning the cup.  Anyway I just purchased
a little blow up pool.  It would be a perfect cheap hot tub in the
winter time.   I just wanted to know if I can get enough heat out of a
waterbed heater to do any good.  I dont really know how to insulate
the pool at this time.   Its only a vinyl blow-up style pool.   I
guess, I could construct a wooden frame around the pool and fill it
with packing penuts.  j/k.  Seriously,  I would like to know how its
going.

thanks, 
Brandon