Check valves on your water heater

[Steelaway35]

What kind of a check valve do you use for your hot water tank?

My tank is a Seaward S600 6 gallon tank with the supply line running horizontal from the pump to the tank. I'm installing my water pump and supply lines next week and would love to hear some ideas.

Thanks!

Kevin

[Kettlewell]

I don't believe I've ever had a check valve in the supply line to the hot water tank. Obviously, the pump is designed to prevent backflow and that is all I've ever had.

[Bash]

Check valves are in the pump, not the tank.

[steamgoat]

If the cold faucet supply is 'T'd off the line between the pump and the heater, a check valve just before the heater will prevent hot water migrating back to the cold faucet. Bruce.

[sailvayu]

A check valve also prevents water from draining from the tank. This can be a very good thing to save the life of your heater element should the heater be turned on before the water system is pressurized.

[sailorchic34]

As Bash said, the check valve in the pump will prevent the tank from loosing water. Standard practice should be that the water pump is switched on and flow checked that there is no air in the system, before turning on the water heater element.

This would mainly be a problem after a winter layup or storage and not really a problem in boats used all the time.

Now if you have a newer VSD water pump, a check valve may sometimes be required in the cold water to the heater. But you would need to add a thermo-expansion tank/ accumulator after the check valve to give the expanding water from heating somewhere to go. That's why even with a VSD pump you still need an accumulator to act as an expansion tank.

For those with an old style on/off water pump a check valve at the tank does not do much.

[Steelaway35]

I'm looking at teeing off of the cold water pressure system and installing the check valve right before the water heater. Right now I'm looking at two different styles of check valves: a spring loaded poppet check valve and a swing check valve, unless you guys know of any other styles that are worth looking at. I'm leaning towards the spring loaded poppet because it can be installed at any angle while the swing check valve's are specific to certain orientation (vertical/horizontal).

I'll be using a variable speed water pump with no accumulator tank and will have the pressure relief valve plumbed into the bilge to deal with excessive pressure build up.

I'm still trying to wrap my head around all the different ways to install a quality plumbing system on my sailboat. I really appreciate your input.

[125Miles]

This is what I have DesignHeating.com - WEBSTONE SWEAT BRASS SWING CHECK VALVES Installed right at the COLD water inlet to the water heater. It stops hot water escaping in to cold water line. I was messing with it trying to figure out what is this device for and it got stuck open. Hot water was coming out of cold water faucet but only for a few seconds. A little annoying plus waste of fresh water. Took me a few years to find out whats wrong The pump gets water from fresh water tank then there is a T split right after, one line goes to water heater the other to cold water circuit. I do have expansion tank as well, just don’t remember where exactly. This is original system from late 80s Sabre.

[sailorchic34]

Originally Posted by Steelaway35

I'm leaning towards the spring loaded poppet because it can be installed at any angle while the swing check valve's are specific to certain orientation (vertical/horizontal).

I'll be using a variable speed water pump with no accumulator tank and will have the pressure relief valve plumbed into the bilge to deal with excessive pressure build up.

Use a swing check. either in upright or horizontal is fine, just not down. pressure from the water heater will keep it closed.

Not a big fan of using T&P reliefs to relief pressure. Oh it will work fine. But two things worry me. First the T&P may get a piece of mineral stuck in the seat and not reset, which could lead to a bilge full of water or an empty water tank.

Second I don't trust the typical aluminum pressure tanks used in the cheap marine heater. I'm thinking that repeated cycling of the tank pressure that normally sees 40-50 psig to 80-100 psig would tend to weaken the tank seams and cause premature tank failure of the aluminum tanks. That's not a problem with the better, IE more expensive glass lined steel tanks of the higher end marine heaters.

If it were me, I'd put a thermal expansion tank somewhere down stream of the check valve and that will prevent excess pressure on the water heater tank. I know the marketing hype of the VSD pumps say you don't need one and you don't for the pump. But they also act as a thermal expansion tank too and if you have a check valve on the heater, (oddly enough sometimes required by the VSD pump) then prudent design would have a expansion tank on the heater too.

Now as someone who has designed 1000's of hot water heating systems up to 1000 GPM (steam fired on that one and no its not a typo) over 30 odd years, I would not put a check valve on the water heater. Well not on a boat. But then I'm not that fond of using small VSD pumps, that cost more and tend to fail faster, due to the more complicated electronics on the VSD side either.

If you don't have a VSD pump you don't need a check valve at the water heater. Worst case,you just need a heat trap (vertical 12" ish U Bend) on the cold side. Simple and nothing to fail.

Check valves fail so if you can avoid using one, its always better....

[125Miles]

+1 on swing check, minimum moving parts, no springs or rubber seals involved, very basic build and anytime you need to empty water heater for winterizing just unscrew the cap and drain all the water. I said earlier there is expansion tank in my system that is not quite right, it rather called accumulator tank. It looks just like this one Amazon.com: Jabsco 30573-0000 Marine Pressurized Water Accumulator Tank with Bladder (1-Liter): Sports & Outdoors serves a bit different purpose. Its more like if I shut off the main breaker and come back to the boat in a week there is always water pressure in the system no matter if pump is running or not.

[sailorchic34]

Actually an accumulator is just a type of expansion tank. Really there is no appreciable difference between the two. They just call it an accumulator at the marine store and charge a bit more for the name...