Hot water heater ck valve

sdrtile · 01-25-2020, 06:54 AM

Just replaced a leaking valve going into the hot water heater. All is fine but my plumber didn't put back the ck valve. Water is on and all is working fine. So do I need the that ck valve?
How important is it? Thanks

Goodspike · 01-25-2020, 07:13 AM

It's there to prevent your tank from exploding. All hot water heaters have these safety devices.

It may be less important with a motor home/travel trailer because something in the plumbing will probably go before the tank actually explodes, but then you'd have something to fix.

Goodspike · 01-25-2020, 07:15 AM

Video.

https://www.youtube.com/watch?v=l3i_ZGPtm68

Morich · 01-25-2020, 08:00 AM

From these two posts, I suspect there is some confusion. Are we speaking of a check valve on the water line? Or the second post refers to the temperature and pressure control, which is a totally different item.
The second post is correct in that the temperature and pressure valve is very important, The check valve is not one that I know much about but is going to be a seperate item.

This is a link to a pretty lame blog which shows the difference in the two item:
https://liveworkdream.com/2018/08/01...r-check-valve/

Note: I call it lame because of the lack of expert advise which it shows. Nothing wrong with going with what you have to get the job done but it is like many of the online items we see, in that this person lacks lots of the experience needed to know how to do things.
He eventually gets the job done but that is after taking the whole thing out and just having along extention on his socket would likely have saved him a ton of work!

Goodspike · 01-25-2020, 08:03 AM

Quote:

Originally Posted by Morich

From these two posts, I suspect there is some confusion. Are we speaking of a check valve on the water line? Or the second post refers to the temperature and pressure control, which is a totally different item.
The second post is correct in that the temperature and pressure valve is very important, The check valve is not one that I know much about but is going to be a seperate item.

Could be--I'm not familiar with what the check valve is if it's not the pressure valve. The only valves I'm familiar with on the water heater are the pressure release valve and the three valves that are part of the bypass system. The latter makes winterization easier.

Is there a flow restriction? I could see that would be necessary if the main water tank was not full. Water might flow from the hot water tank to the main tank if you didn't have the pump on or have water connected.

emiddleb · 01-25-2020, 08:15 AM

Yeah, you are talking two different things. The pressure relief valve (has a small lever on it) prevents the water heater from exploding. Critical that it works properly and should be checked every now and then.

The check valve(s) are usually on the back of the water heater. Most have one on the cold input line, some have another on the outflow hot water line (mine has both.) The primary purpose is to allow water to only flow one way... cold into the water heater, hot out to the faucets. The check valves keep the hot water from backflowing into the cold water system. Critical.. no but desired. They do serve a purpose in helping to maintain appropriate pressure in the heater and preventing any contamination from the water heater getting back into the cold water system. As the water heats in the heater it creates more pressure, and without the check valve the hot water can backflow into the cold system. Personally, I'd replace it, but you can run without it.

Goodspike · 01-25-2020, 10:24 AM

I think it might depend on how you travel. If you always have water connections and travel without any water in the tanks, no valve could be an advantage because the hot water tank could also be drained. If not, or if you don't care about the weight of the water in the tank, I would want the valve.

Morich · 01-25-2020, 11:32 AM

Check valve may be confusing term to some but a simple way to think of it is as a one way valve as it restrict flow in only one direction. doesn't stop water from draining but it does keep the water that is heated in the heater, so it does some things that most of us would want. It saves us letting hot water go into the cold water and that can be important if you are getting a drink and don't want to find warm/ hot water coming out of the cold faucet and it also helps save fuel if we only heat the water and hold it instead of letting it fill the lines in the RV. In the pictures in the link, the check valve is the small brass item which is inline with the flow, while the temperature and pressure valve is just screwed into the tank side where it can pop off if the temperature or pressure get too high. For my use, I would certainly be talking to the plumber about redoing the job if either is left off.
I've never had any trouble with the check valves but they could certainly become a problem if run lots of minerals or other debris through them.

rarebear.nm · 01-25-2020, 06:11 PM

Quote:

Originally Posted by sdrtile

Just replaced a leaking valve going into the hot water heater. All is fine but my plumber didn't put back the ck valve. Water is on and all is working fine. So do I need the that ck valve?
How important is it? Thanks

Are you referring to the pressure relief valve on the outside portion of the WH or a check valve on the interior side?

If it's the pressure relief valve it is important for safety reasons. If it's on the inside, is it on the cold input or the hot output side of the heater? A check valve is frequently used on the hot side as part of the winterization by pass system. Not sure why there would be a check valve on the cold input side. Also a check valve on the hot side may help prevent a cold blast of water in the shower if you use the shut-off valve at the shower head and then turn it back on. I've added check valves on the hot line as close to the shower as I can get it for this purpose. It really solves that problem.

imnprsd · 01-25-2020, 07:09 PM

Everyone seems to have their own opinion on the function and purpose of the check valve, so I will share mine:

* Those check valves fail all the time and they always seem to fail in the middle of your trip. They are a PITA and you really don't need them at all.

* Both my check valves failed and I saved money and time by reusing them... after I drilled the guts out of the center and then reinstalling them. This fixed my hot water problem (hot water in the tank, but only cold water coming out the hot water side of my faucet), and have been happy-happy every since.

Also drilling out your old check valves does not cost you anything. And in my case it's hard to find a replacement. Just be prepared to unscrew these check valves with a 1-1/8" long wench (maybe 1-14"???), because a large crescent wrench may not give you enough leverage to unscrew the "nipple".

* You also will need a couple "donuts" replacements for the plastic side of the nipple. And be sure not to over tighten this side or the plastic may crack.

* Their purpose is to prevent back flow or winterization-anti freeze from entering the coach. And since anti-freeze is corrosive when it comes in contact with aluminum this may explain why you may see black flecks in your water tank when you clean it out.

This corrosion is not a problem for an aluminum tank unless you leave your antifreeze in the hot water tank for over 1 year or more. I did this once by mistake, and after letting a lot of the "pink stuff" sit in my aluminum HW tank I just found a lot of black flecks the next season. As for what the "pink stuff" does to a steel HW tank I can't tell you. (Who knows the answer?)

* If you properly winterize you tank and are sure no cold water will enter your hot water tank, because you shut off the water flow correctly, then you are 90% likely to never get antifreeze into your HW tank through the cold water line-in side... located at the bottom of the HW tank. (See diagram.)

* And if you don't evacuate you water lines before you winterize your coach, using the siphon method of drawing antifreeze into all your water lines, then you will probably NOT get any antifreeze into your HW tank through the hot water side of your tank.

So cold water enters the tank from the bottom... then the water is heated... then the water expands... and the pressure re-leaf valve is there as a safety measure. Note: Hot water is less dense than cold water so it rises to the top of the tank, but under pressure inside the tank this process is not as effective... and so you get spurts of cold water entering the top tub... which sits just below the water line.

Note: So if you are camped for more than 3 weeks and your hot water is not as hot, then maybe you just need to open your pressure re-leaf valve to let some water out. This will also increase the air gap and your HW tank will again reach "equilibrium."

FYI, the shower is where you will first notice the temperature change, because the hot water out of the tank goes to the shower first... then to the bathroom sink, and then to the kitchen sink. (At least it does in my 40' Itasca "Horizon."

This is why I winterize the shower first... then turn off the shower valve... then I move on to winterize the bathroom sink... and then the kitchen sink; in this order so I don't use anymore antifreeze than I need to. (I can winterize my coach with 2 gallons of the "pink stuff" but first timers may need 3 gallons... especially if you need to winterize your washing machine.

Anyway, with the check valves gone (drilled out) you have a chance of antifreeze entering the HW tank, but I really don't care.

And don't forget you want enough pink stuff to come out of the faucet so it can fill the P-trap.

ftodaro · 01-25-2020, 07:32 PM

I just posted in another thread about my experience in replacing my hot water tank. I replaced the check valve at the same time as i was in there and that is the time to do it. But as stated above the check valve is helpful when it comes time to winterize your tank. If you have a winterize bypass valve the check valve prevents it back filling with antifreeze.

NeilV · 02-02-2020, 08:28 PM

Quote:

Originally Posted by sdrtile

Just replaced a leaking valve going into the hot water heater. All is fine but my plumber didn't put back the ck valve. Water is on and all is working fine. So do I need the that ck valve?
How important is it? Thanks

The check valves prevent reverse flow back into the cold water system so you do not end up with hot water coming out of the cold water faucets or hot water circulating into the fresh water tank. They can save propane too by limiting the natural flow of heat back up the cold water feed line.

gewilli · 02-02-2020, 10:03 PM

Not exactly, check valve is different than pressure relief valve.

C Zimm · 02-03-2020, 02:28 PM

NielV is right on. Why would anyone want to send hot water to the fresh water tank?

imnprsd · 02-04-2020, 01:07 AM

I think it's practically impossible for hot water to enter you cold water tank... if your thermostats are working properly... and you drill out the guts of those worthless check valves!

Remember, those thermostats are physically mounted to the tank side wall... at particular height. They turn On & Off the heating element and/or the gas heat if you have two ways of heating your hot water... when the hot water grows from the top of the tank DOWN to bottom of the tank.
So the physical placement of those thermostats are important. And IMO there is no chance for hot water will mix with the cold water in the storage tank.

Or to say it another way, cold water is being PUSHED into the tank ...at the bottom; and hot water is PUSHED out the top of the tank.

You can confirm this by noticing the top of the tank is hot and the bottom is luke warm.
Remember, hot water is less dense than cold water so it rises to the top of the tank.

Note: Some people find their 3-way valve causes problems with hot water delivery. So if your valve looks like the one below (like I have on my Itasca "Horizon" then you probably need to order it on Amazon; and I mention it because I could not find it at 4 different RV stores when I was having hot water trouble... which turned out to be a stuck check valve.

Flair-It Hot Water Valve #16910 Plastic 3-Way Valve

Mike Owens · 02-04-2020, 08:24 AM

The check valve is there to prevent the reverse flow during a pressure change in the system. Now will it flow enough to start heating up your cold water tank, not likely. Will it waste energy, yes. The example that comes to mind it lets say someone is using the hot water mixed with cold. Like a shower... A opening of a cold water valve, toilet or sink, will change the pressure in the system. The cold just got lower more than likely. Now for the time the pressure changes the hot can travel back without the check valve. Is it allot, no, does it inconvenience the person in the shower, yes. Is it a huge deal, depends on how you use the rig and how many are using things in the water system. I would replace it because the people who put it there know more than me about the design of the system.

CharlesMoore · 02-04-2020, 09:10 AM

There some elgant answers and pictures here. Since I just had to have my Atwood 10 gal hotwater heater replaced I thought I would comment. The RV repairman, at great difficulty, removed and replaced my original 2002 hot water heater with a new Atwood of similar model. Due to space requirement limitations with a slightly different rear tank layout we did not put a check valve in the water inlet. The system works fine without it and there is no transfer of hot water into the cold lines.

Every year we drain the hotwater tank and "blow" the waterlines with low pressure air (about 20 -30 psi). This eliminates the "pink stuff" except for drain traps and toilet. It is really quite easy and takes me about 30 minutes or less ( I blow the lines twice ). Sometimes as the travel situations dictates, we do this procedure 2 or three times. I bought a inexpensive Harbor Freight compressor for the process and we carry it everywhere we go.

I do have two switches/solenoid that bypass the hotwater and switch the house water pump such that the pump pulls "pink stuff" and distributes it through the water system. This process takes about the same time as "blowing" the lines. Eventually we just gave up on this process and only use air to clear the system of water.

Goodspike · 02-05-2020, 08:49 AM

Unless it's impossible for water to flow backwards through the water pump, I think the main concern of reverse flow would be when the pump is off and there's no connection to city water. In that scenario if the water heater fill level were higher than the fresh water tank fill level (probably fairly likely on most vehicles) you'd get back flow any time someone opened a hot water valve (again unless water cannot flow backwards through the pump). That could conceivably lead to burned out electrical elements if plugged in and on electric heating of the water.

In other contexts you can get backflow out of a hot water system if you have both valves open on a faucet with a single connection, but I don't see that being a huge issue with motor homes/travel trailers. I lived in a high rise once where pressure differences overwhelmed circulation pumps for the hot water system.

As someone above mentioned, the people who designed the system to include these check valves know a lot more about the system than us.

imnprsd · 02-06-2020, 08:14 PM

When it comes to hot water heater check valves, IMO, you can give "smarter people" the benefit of the doubt, but then you would have to believe theory is more important reality!

And let's not forget the millions of dollars made in unnecessary service repairs these failed check-valves cause; and the untold number of days coach owners had to go without hot water or got scalded by a partially stuck check valve.

Facts are: Check-valves are necessary! ...And having a hot water check value does not protect you from getting scalded... just the opposite. A partially stuck check-valve can cause scalding.

So why are check-valves installed?

IMO, they are a holdover from the days when coach manufactures did NOT provide winterizing controls. ...But for us Class A owners, who have separate winterizing controls, these check-valves are a PITA; and I would advice everyone with separate winterizing controls to drill-out the guts of those check-valves anytime it fails.

Not to mention, there are numerous reports from owners who have replaced these check valves multiple times too! Don't believe the doom and groomers. Get rid of those check valves and buy a couple 50 cent rubber donuts to mate the plastic to the metal nipple.

...Just re-use those drilled out check-valves so you don't have to buy pipe-nipples. ($0)

Goodspike · 02-07-2020, 07:52 AM

Quote:

Originally Posted by imnprsd

When it comes to hot water heater check valves, IMO, you can give "smarter people" the benefit of the doubt, but then you would have to believe theory is more important reality!

House water heaters have check valves too. I know because the one on my tank makes noise. It has nothing to do with winterization.

And I don't see how a check valve could cause scalding--seemingly it would be just the opposite. It affects the hot water side, so it could cut off the hot water side but doesn't cut off the cold water supply. And it prevents hot water from running into the cold water pipes (a situation which could cause scalding). Please explain your theory on that how it causes scalding.

I had assumed peoples' complaints about these valves were that they would malfunction and reduce hot water flow.