Date:         Sun, 05 May 1996 18:17:13 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         jwakefield@4dmg.net (john wakefield)
Subject:      Re: 83 Sink's 12V water pump

First of all, I want to say thanks to Jim of BusBoys@aol.com for his very 
instructive discussion of sink water pumps, their history. and current 
pricing.
  Now I'd like to hear a few words about the trade-offs beyond price between 
the immersible water pump (V@L members' price $44.96US) and the 
outside-the-tank pump (V@L member's price $35.96US).
  Clearly the immersible pump is self priming.  Is the outside-the-tank pump 
also a self primer?
  How about comparing flow rates and your best guess as to which is likely to 
have a better life expectancy.
  Water getting where it's not intended is another issue.  With my old 
immersible pump, it got up into the pump motor, even though it's 
surrounding case is designed to trap air in its top to keep it dry.  I urge 
those servicing these immersible pumps to make certain its bottom stays down 
and its top stays up, and don't let it lay on its side at your tank's bottom 
or you'll allow water to flood the entraped air space where the motor hides 
behind an attempt at sealing the rotating shaft.  Don't turn it upside down 
while it's wet.  I could hear water sloshing inside the "sealed" motor 
compartment.  I remember my "BAR Maid" brand submergible glass washers that 
cleaned beer and mixed drink glasses.  Their motors ran in an inverted sealed 
oil chamber like this.  True, the drive shaft seals were good, but the elegant 
design feature was the fact that the density of the oil was less than the 
surrounding water, so they never got wet and they never introduced a drop of 
oil into the "beer clean" (and that's damned clean) water.  The speed would 
drop, but you'd get tired waiting to wear out one so modified IMO.  Also, the 
pick-up leading to the impeller must be at the bottom to pump the last 
available water from the tank.  On the other hand, the immersible pump can't 
leak outside because it's inside the tank.
  I haven't seen the outside-the-tank style pump nor do I know if it's 
identically fead from the tank top.  Does it have a "dry on one side wet on 
the other" water seal between the motor and pump that's subject to leaking, or 
is it a diaphram and check valve design?  That's what my Blue Bird Wanderlodge 
bus has, and they're supposed to be quite free from leaking problems.
  At this point, my options are open and unless I find a good high/low speed 
pump, I'll probably go with which ever seems the best, but I still need more 
information to decide which I think is best.  Thanks for any responses.

	John Wakefield