• Annnnnnd we're back! Got questions, suggestions, or comments, Guest? Post them here!

Tempering Valve Recommendation?

Feb 5, 2004
3,660
Tartan 3800 Westport, MA
What make/model tempering valve you do have, or recommend?

Our hot water is often too hot. I want to install a tempering valve. However, the one I thought would work well has a recommended minimum pressure of 30 psi, and my system runs from 20 to 40. It also has check valves on both sides, necessitating an expansion tank on the hot side.

Any ideas?

Thanks,

jv
 
Apr 3, 2019
272
Macgregor 26M P Cub Boo Mobile AL
You might check Leonard 270-LF. They don't specify a minimum pressure requirement. Data indicate that at 5 psi drop, it will pass 3.5 gpm if I recall correctly. Min flow is 0.25. Looks like range is about right for your intended use.

I'd be tempted to call them first if you plan to run at 20psi supply pressure. I've never done a system with a supply pressure that low.
 
Feb 5, 2004
3,660
Tartan 3800 Westport, MA
I'd be tempted to call them first if you plan to run at 20psi supply pressure. I've never done a system with a supply pressure that low.
The pressure switch on the pump runs between 20 and 40 psi. I thought that was pretty standard.
 
Apr 3, 2019
272
Macgregor 26M P Cub Boo Mobile AL
Understand. I designed building systems; research, military, medical, aircraft maintenance, etc. The 20-40 psi range is outside of my experience base for hot water systems with thermostatic mixing valves. Don't want to misrepresent my expertise in this instance.
 
Feb 5, 2004
3,660
Tartan 3800 Westport, MA
Understand. I designed building systems; research, military, medical, aircraft maintenance, etc. The 20-40 psi range is outside of my experience base for hot water systems with thermostatic mixing valves. Don't want to misrepresent my expertise in this instance.
Yea, no worries, I appreciate the input. I'm just learning about this stuff.

One concern is that the tempering valves all seem to have check valves, necessitating I install an expansion tank on the hot side (the cold already has one). Does this make sense to you?
 
Jan 11, 2014
4,055
Sabre 362 113 Fair Haven, NY
Yea, no worries, I appreciate the input. I'm just learning about this stuff.

One concern is that the tempering valves all seem to have check valves, necessitating I install an expansion tank on the hot side (the cold already has one). Does this make sense to you?
No. The one I listed does not have a check valve. It is a solder connection, however, if you search around Watts makes one with threaded connections.
 
Apr 3, 2019
272
Macgregor 26M P Cub Boo Mobile AL
They are often installed in systems with circulation pumps, which can create unintentional flows in various directions. Also, thermal siphoning (convective flow) can create undesired heating in the cold water line. They are likely trying to maintain good separation of the hot and cold supply lines so that the valve can maintain reasonable temperature control.

I'm spitballing here. I have never asked the question to a manufacturer before. So, take it with a box of salt.
 
May 20, 2016
2,792
Catalina 36 MK1 Everett, WA
[QUOTE="jviss, post: 1554269, member: 66876”]

One concern is that the tempering valves all seem to have check valves, necessitating I install an expansion tank on the hot side (the cold already has one). Does this make sense to you?[/QUOTE]

Nope the one on the cold side should be all you need. If not install a bigger one. One on the hot side just means a longer wait for hot water and more water down the drain.
 
Oct 22, 2014
9,926
CAL 35 Cruiser Portland OR, moored EVERETT WA
Adding to what Les has stated, your hot water tank serves as an expansion tank. It is in line after the accumulator (serving as an expansion tank). The accumulator serves to mitigate the sensitivity of the water pump. If yours is like most systems there is a check valve between the cold water in and the cold water inlet of the water heater. This is designed to stop the back flow of hot water into the cold water line. You should not need additional check valves.
 
Jan 22, 2008
7,032
Beneteau 323 Annapolis MD
I have neither check valves added nor expansion tanks. It all works fine. I find after a night on the hook the water in the morning is hotter and more plentiful.
 
Apr 3, 2019
272
Macgregor 26M P Cub Boo Mobile AL
Yea, no worries, I appreciate the input. I'm just learning about this stuff.

One concern is that the tempering valves all seem to have check valves, necessitating I install an expansion tank on the hot side (the cold already has one). Does this make sense to you?
@jviss , were you asking about the internal checks or the need for an expansion tank on the hot side? If it's expansion tanks, we'd have to review your piping arrangement first.

Sorry if I missed your question.
 
Apr 3, 2019
272
Macgregor 26M P Cub Boo Mobile AL
You should not need additional check valves.
I think he was referring to the internal check valves that are part of the tempering valves. As usual, you try to fix one problem and it creates other situations you need to consider. Or, with my luck, you turn over a rock and find a whole quarry underneath...
 
  • Like
Likes: jssailem
Oct 22, 2014
9,926
CAL 35 Cruiser Portland OR, moored EVERETT WA
I understand you thought @Jim26m. You are correct.
What I was stating was that the general boat systems do not have the additional detailed expansion tank check valve structure that you find in your medical or military projects. Not that they could not be used, it is just not done in the lower tech designs of boats due to the need to limit costs.
The low tech systems serve 98%of the need ( this percentage is opinion based on personal observation of a large number of boats in the under 48 foot category).
 
  • Like
Likes: Jim26m
May 24, 2004
5,854
CC 30 South Florida
I thought that is the way it was with marine water heaters and I just learned how to live around it. Never use hot water immediately after the engine has been running for long and turn the Water heater breaker On just 15 minutes prior to use when on shore power. No big deal, have taken so many cold water showers it is of little importance to me.
 
Apr 3, 2019
272
Macgregor 26M P Cub Boo Mobile AL
With a six gallon tank, you can't take a 45 min shower. Otherwise, the system should be able to self regulate and provide consistent hot water temperatures whether on shore power or using engine heat.

Adding the tempering valve will allow safely running the tank hotter, effectively giving you more usable hot water (since you're mixing more cold water with it when you use it). Keeping the tank at 140-160 would be very dangerous without a tempering valve - particularly with kids or anyone with impairment or lack of heat sensation.

@jssailem, I think @jviss is concerned that if he adds new check valves in his system, as part of his tempering valve assembly, he may wind up with an over-pressure problem. It hasn't been too long since we worked through an over-pressure issue on a hot water system for another boater. That turned out to be caused by a check valve that the owner was unaware of.

Depending on how his system is piped and where he installs the tempering valve, he may or may not have an overpressure issue. But, it's always best to review the system schematic carefully, with your modifications drawn in as you intend to install them - before you start cutting pipe.. I'm sure he's already thought of this. Even though these systems don't get terribly large, they can have some of the same issues that larger systems have.

You know how we are: if it still works, we haven't added enough features.:cool: