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Re: Tankless whole-house water heater

To: shop-talk <shop-talk@autox.team.net>
Subject: Re: Tankless whole-house water heater
From: Darrell Walker <darrellw@ipns.com>
Date: Thu, 2 Mar 2006 14:33:28 -0800
Thanks everyone for the information/opinions on tankless water  
heaters.   It looks like if I go this route, I will at least have to  
have a new gas line run, since the existing heater is only on a 1/2"  
line and the size unit I would get would need at least 3/4", if not  
1".  I also have to figure out the venting options, as the existing  
galvanized vent won't work (I wonder if the 3" stainless vent could  
be run inside the existing 4" vent?).

Anyway, all of this discussion brings up another plumbing issue in my  
house.  I suspect it is a design flaw of some sort, since it has  
always been this way.  The problem seems to be with the balance of  
hot/cold (for lack of a better term).  If you are taking a shower  
with the temperature set comfortably (for me, that is about 60% hot/ 
40% cold water, assuming the valve is fairly linear), any other water  
usage in the house (either hot or cold) will radically affect the  
temperature in the shower.  For example, if someone flushed the  
toilet, the shower gets very hot.  Even minor usage on just cold  
water, like the water dispenser on the fridge causes a noticeable  
temperature change.  Conversely, any other hot water usage will make  
the shower noticeably cold.

At first I thought it was pressure related, but it wouldn't that  
effect the hot and cold supply somewhat evenly?  The only other thing  
I can think of is that the plumbing is laid out such that the showers  
are  near/at the ends of the pipe runs, such that the other fixtures  
are essentially pulling water out upstream, and the plumbing isn't  
sized to deal with that.  If that is the case, the there seems little  
hope if fixing it short of running new water pipes.  Any other  
possibilities of causes?

Thanks!

-- 
Darrell Walker
66 TR4A IRS CTC67956L
Vancouver, WA, USA




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