Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 13-07-2015, 20:15   #1
Registered User
 
malbert73's Avatar

Join Date: Jun 2008
Boat: Tartan 40
Posts: 1,032
hot water out of cold faucet- why?

Hi everyone,
This happened on my old boat as well- and I am a bit mystified.

Especially when hot water tank is freshly hot, my shower and galley sink take a lot of running to get cold water out. I'll have diverter handle on galley sink all the way to cold and it will remain burning hot for 10-20 seconds until it finally runs cold. Then if I turn it off to wash more dishes, same happens. Water temps also fluctuate a lot in shower when turning on and off at shower head. I thought this was the mixer valve but same happens at shower where I have separate hot and cold water knobs. I have a single water pump, and an accumulator tank.

Is hot water somehow backing into cold water plumbing, needing to get flushed out? I'm a bit stumped on how (if at all) to fix this to prevent scalding and improve shower quality. Saving water would be nice also.
__________________

__________________
malbert73 is offline   Reply With Quote
Old 13-07-2015, 20:23   #2
Registered User

Join Date: Jun 2013
Posts: 171
Re: hot water out of cold faucet- why?

Water system runs through the engine room everything gets hot

Sent from my SM-G920P using Cruisers Sailing Forum mobile app
__________________

__________________
Bohemian17 is offline   Reply With Quote
Old 13-07-2015, 20:23   #3
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,826
Re: hot water out of cold faucet- why?

Hot and cold lines in a common insulated wrapping?
Possibly to prevent freeze damage?
__________________
Memento,homo, quia pulvis es, et in pulverem reverteris.
senormechanico is offline   Reply With Quote
Old 13-07-2015, 20:24   #4
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 5,766
Re: hot water out of cold faucet- why?

Check valve on the cold inlet side of the water heater should cure this.


Sent from my iPhone using Cruisers Sailing Forum
__________________
Sailmonkey is online now   Reply With Quote
Old 13-07-2015, 21:15   #5
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,385
Re: hot water out of cold faucet- why?

Many times H&C hoses are wire tied together. Guess what happens.
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is online now   Reply With Quote
Old 13-07-2015, 21:25   #6
Marine Service Provider
 
Scott Berg's Avatar

Join Date: Jul 2011
Location: Aboard
Boat: Seaton 60' Ketch
Posts: 959
Re: hot water out of cold faucet- why?

ditto on the check valve (there should be one on the cold water going into the heater)

This can also cause water to swing from hot to cold.. they do go bad...
__________________
Scott Berg
WAĜLSS
SV CHARDONNAY
Scott Berg is online now   Reply With Quote
Old 13-07-2015, 22:42   #7
Moderator
 
sailorchic34's Avatar

Cruisers Forum Supporter

Join Date: Feb 2011
Location: SF Bay Area
Boat: Islander 34
Posts: 4,812
Re: hot water out of cold faucet- why?

DO you have an accumulator/expansion tank on the water system. What is most likely happening is as the cold water in the tank heats up it expands quite a bit, this with the accumulator will cause hot water to back up into the cold water line. To prevent that. Move the accumulator to adjacent to the water heater. That will keep the expanding hot water local to the heater.

The other think that could be happening with engine heating is a thermo-syphon where hot water rises and cold water falls. Normally that would be on the hot side. But if the water heater is hot and there is a cold water faucet above the water heater, you can get thermo-syphon on the cold side.

Specially with a horizontal heater. Adding a check valve at the heater cold water line will prevent that. Best to add an accumulator between the check valve and heater to prevent excess pressure in the tank.
__________________
sailorchic34 is offline   Reply With Quote
Old 14-07-2015, 06:58   #8
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
Re: hot water out of cold faucet- why?

Can you put some heat insulation from the hot water transfer heater outward hose to the sink?

Mine both hoses, hot and cold run touching each other. after the engine is on for a bit the hot water hose heats the cold water hose.
__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Old 14-07-2015, 09:41   #9
Registered User

Join Date: Jul 2013
Location: Annapolis, MD, USA
Boat: Menger 19' Catboat
Posts: 248
Re: hot water out of cold faucet- why?

Yep, it is likely the proximity of the hot and cold lines to each other near the water heater. I had this problem in my old liveaboard cutter until I replaced the original water heater and rerouted the lines. It was exceptionally bad in my case because the lines were copper, enhancing the heat transfer.
__________________
Ukeluthier is offline   Reply With Quote
Old 14-07-2015, 10:19   #10
Registered User

Join Date: Apr 2015
Location: West Coast FLA
Boat: 1978 Pearson 424 Ketch
Posts: 451
Re: hot water out of cold faucet- why?

Quote:
Originally Posted by Sailmonkey View Post
Check valve on the cold inlet side of the water heater should cure this.


Sent from my iPhone using Cruisers Sailing Forum
this is the common cause. most boats have this check valve, but they do go bad and leak back somewhat. Cleaning or replacing would be in order. I don't go for replacing right away cleaning works quite often. being next to large temp deference will cause calcium buildup. pull it out and soak it in white vinegar for a couple hours and scrub it with a soft brush. don't mar the mating surface of the valve disc and seat.
__________________
tinkrman69 is offline   Reply With Quote
Old 14-07-2015, 11:05   #11
Registered User
 
malbert73's Avatar

Join Date: Jun 2008
Boat: Tartan 40
Posts: 1,032
Re: hot water out of cold faucet- why?

Thanks everyone for the input. Definitely not the hoses touching each other. When I mean hot- it is scalding, steaming hot coming out of cold water faucet. Hotter than outside of hot water tubing ever gets.


There is no check valve at my cold water inlet to hot water heater that I can see. There was not one on my old boat either, which had same problem. So I am hearing that hot water leaks back into the cold water line until the pump and then gets pushed out to the faucets?

I have an accumulator tank, though it's not close to hot water tank. That shouldn't matter, right, since backpressure will equalize along water line?

Any other ideas? I will be installing a check valve as soon as I find the right one. Would be amazing if it's that easy.
__________________
malbert73 is offline   Reply With Quote
Old 14-07-2015, 11:08   #12
Registered User
 
CaptTom's Avatar

Join Date: Apr 2004
Location: Southern Maine
Boat: Prairie 36 Coastal Cruiser
Posts: 971
Re: hot water out of cold faucet- why?

I just added a check valve on the cold (input) side of the water heater and solved the exact symptoms the OP describes.
__________________
CaptTom is online now   Reply With Quote
Old 14-07-2015, 11:32   #13
Registered User

Join Date: Apr 2015
Location: Perth Australia
Posts: 12
Re: hot water out of cold faucet- why?

Is your f/w pump cycling? I've seen plastic impellors deform from the heat build up in the water from friction .
__________________
capt jolly is offline   Reply With Quote
Old 14-07-2015, 15:04   #14
Registered User

Join Date: Sep 2014
Location: New London, NH
Boat: Intrepid 9 meter, 29.5 feet
Posts: 91
Re: hot water out of cold faucet- why?

A check valve in the cold water line to the hot water tank probably will solve the problem of hot water where cold water should be, but suggests a new problem. As noted, the hot water expands a lot. Your hot water heater should have a pressure relief valve. Mine isn't plumbed anywhere. Where do you want your excess hot water to go?
__________________
Old Swampy is offline   Reply With Quote
Old 14-07-2015, 15:46   #15
Registered User

Join Date: Apr 2015
Location: West Coast FLA
Boat: 1978 Pearson 424 Ketch
Posts: 451
Re: hot water out of cold faucet- why?

The accumulator should be the first thing inline from the pump then the "T" that splits off to the cold water manifold and the check valve to the cold water inlet to the hot water heater, then the hot water manifold out of the heater.

When the engine is runing the water will get up as high as 180 deg. depending if your engine is fresh or raw water cooled. raw water cooled engines run cooler.

If you don't have a check valve, then install one. it should be bronze or brass tho, as synthetic ones won't handle the heat over time. you can put hose to its inlet side, but it's preferable to use hard pipe from it to the hot water heater inlet

I use hard pipe al the way to the "T" and hose to that and the cold water manifold
__________________

__________________
tinkrman69 is offline   Reply With Quote
Reply

Tags
water

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
HOT HOT HOT! running AC on Honda generator sailorboy1 Plumbing Systems and Fixtures 12 09-07-2013 18:07
Fresh and Sea Water Faucet in One in the Galley Idea ... Ocean Roads Plumbing Systems and Fixtures 34 14-12-2012 09:47
Hot water pressure but not cold Neo Plumbing Systems and Fixtures 2 31-07-2012 10:10
Hot Water System - Extra Hot Water Needed ? Harben Plumbing Systems and Fixtures 8 07-10-2010 17:20
Ohhhhh Hot! Hot! Hot! knottybuoyz Marine Electronics 6 01-06-2007 08:43



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:08.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.