Reply
 
Thread Tools Search this Thread Display Modes
 
Old 07-19-2013, 12:09 PM   #29
Moderator
 
DKB_SATX's Avatar

 
2017 26' Flying Cloud
1976 Argosy 28
Alamo Heights , Texas
Join Date: Aug 2006
Posts: 6,400
Images: 1
Blog Entries: 7
Quote:
Originally Posted by perryg114 View Post
The problem I am having with shutting the shower all the way off causes really hot water to come out the next time it is operated especially using the pump. I expect a variable flow pump or accumulator would help with this problem. I expect this is caused by the air bubble in the hot water tank that keeps the pressure higher on the hot water side making the hot water flow faster than the cold water side when opening the shower head.

Perry
The flow may differ for various reasons downstream of the pump on the hot and cold sides, but the PRESSURE when the shutoff valve on the shower is closed is going to be equal through the entire system. You'd have to have 2 isolated systems with 2 pumps to have different pressure on the hot and cold sides.
__________________

__________________
— David

Zero Gravitas — 2017 Flying Cloud 26U | Il Progetto — 1976 Argosy 28 Center Bath | WBCCI# 15566

He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill
DKB_SATX is offline   Reply With Quote
Old 07-19-2013, 12:09 PM   #30
Rivet Master
 
TinShack's Avatar

 
2005 28' Safari S/O
Paradise , California
Join Date: Jul 2006
Posts: 3,438
Images: 28
Quote:
Originally Posted by loechli View Post
Thanks I saw that last night online,
Does anyone have this sprayer, does it shut off completely or trickle,
my original 1972 white shuts off completely and we really like that feature.
It's a trickle. Why do I snicker when I say that
__________________

__________________
Steve
"THE OLDER I GET, THE BETTER I WAS"
TinShack is offline   Reply With Quote
Old 07-19-2013, 04:43 PM   #31
Rivet Master
 
1981 31' Excella II
New Market , Alabama
Join Date: Sep 2011
Posts: 5,648
The pressure is the same when there is no flow but as soon as the shower head is opened the pressure in the cold water line drops lower than the hot water side because the hot water tank acts like an accumulator and keeps the pressure more constant. An accumulator down stream of the pump would reduce this. Once the pump starts running, the water temp stabilizes.

Perry

Quote:
Originally Posted by DKB_SATX View Post
The flow may differ for various reasons downstream of the pump on the hot and cold sides, but the PRESSURE when the shutoff valve on the shower is closed is going to be equal through the entire system. You'd have to have 2 isolated systems with 2 pumps to have different pressure on the hot and cold sides.
__________________
perryg114 is offline   Reply With Quote
Old 07-19-2013, 05:09 PM   #32
Moderator
 
DKB_SATX's Avatar

 
2017 26' Flying Cloud
1976 Argosy 28
Alamo Heights , Texas
Join Date: Aug 2006
Posts: 6,400
Images: 1
Blog Entries: 7
Quote:
Originally Posted by perryg114 View Post
The pressure is the same when there is no flow but as soon as the shower head is opened the pressure in the cold water line drops lower than the hot water side because the hot water tank acts like an accumulator and keeps the pressure more constant. An accumulator down stream of the pump would reduce this. Once the pump starts running, the water temp stabilizes.

Perry
I still think you're confusing pressure with flow. There's no backflow preventer between the water heater inlet and the cold lines, so any pressurization that might be provided by the air bubble in the water heater is going to push both directions equally (toward the inlet and outlet) and pressure measured in the hot and cold lines would be the same or so close the difference wouldn't be relevant.

For the system in question (and under any normal conditions) we can consider water to be an incompressible fluid so you'd have to have something that made the hot and cold lines 2 distinct systems to get a pressure difference between them.
__________________
— David

Zero Gravitas — 2017 Flying Cloud 26U | Il Progetto — 1976 Argosy 28 Center Bath | WBCCI# 15566

He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill
DKB_SATX is offline   Reply With Quote
Old 07-19-2013, 06:36 PM   #33
Rivet Master
 
1981 31' Excella II
New Market , Alabama
Join Date: Sep 2011
Posts: 5,648
Don't lecture me on fluid mechanics I have two degrees in it.

Perry
__________________
perryg114 is offline   Reply With Quote
Old 07-20-2013, 12:43 AM   #34
4 Rivet Member
 
TerraYacht's Avatar

 
2005 30' Land Yacht 30 SL
Castro Valley , California
Join Date: Jun 2008
Posts: 335
I noticed no mention of the other variable: the heater for the tank is probably heating so the pressure in the tank will increase compared to the cold water static pressure...if there is a check valve. Otherwise, as noted, it would back-pressure and increase the entire system. However, in my moho, the tank is very close to the shower so there is may be more increase in this short feed. By observation, when I use the valve for zero flow, there is a brief "spurt" of hotter water, so I use the trickle valve.

I'm about to replace my OEM shower head with an Oxygenics. I had one of those in my house a few years ago & really liked it.
__________________
Cliff & Andrea,
2 cats, but they stay home
TerraYacht is offline   Reply With Quote
Old 07-20-2013, 07:22 AM   #35
Rivet Master
 
1981 31' Excella II
New Market , Alabama
Join Date: Sep 2011
Posts: 5,648
Whatever the cause, you can get scalded and that is not good. I have not used my shower much with an external water supply and I am sure that will help with this issue. The main issue with cutting the water all the way off is saving water when you don't have a sewer hookup. There is enough hot water but not enough gray tank to leave it running. The accumulator or variable flow pump or both should help with this. At low water flow the pump is turning on and off and the pressure is all over the place. Getting rid of the pulsation is the fix whatever the exact cause.

Perry
__________________
perryg114 is offline   Reply With Quote
Old 07-20-2013, 08:32 AM   #36
Rivet Master
 
TouringDan's Avatar

 
1966 24' Tradewind
1995 34' Excella
Lynchburg , Virginia
Join Date: Sep 2009
Posts: 2,470
Perry

Scalding water would not be acceptable and I don't know why you have it. I have a low flow shower head, 1.5 gpm I believe, a constant speed pump, no accumulator, and a zero flow shutoff valve just upstream of the shower head handle, see photo. I get a small variation in water temperature when I turn the water on, but no big deal. It is definitely not a problem. The zero flow ball valve works so well that I use it alone to turn the water on and off. I keep the shower flow control valves open and adjust water flow/temperature as needed.

Dan
Attached Thumbnails
Click image for larger version

Name:	STA_0994.JPG
Views:	47
Size:	301.5 KB
ID:	191247  
__________________

__________________
TouringDan is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 12:11 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.