Water heater backflow.

[Dan Listermann]

Our cold water faucets always produce an initial stream of hot water before the cold starts. I believe it has to do with the expansion tank on the heater. There is a check valve on the water line that feeds the heater, but the backflow seems to indicate that it does not work. It is the flapper type and it is pointed down. Is there a problem with trying to use this sort of check valve in a downward position? I checked the arrow marking and it appears to be installed in the right direction.

[bob haller]

might be the cold water line is close to something that produces heat like the water heaters flue? anything that produces heat... even the cold water line close to the hot line.

might be a good idea to go inspect the entire line runs.....

[Bill]

Plumbing can be simple, yet complex.

Yes that type of check valve should be installed horizontal with the hinge portion of the valve up. Then gravity wants to hold the valve in the closed position. Wrong way water flow will instantly be blocked. Right way water flow will have enough pressure to open the flapper.

With that said, water when heated EXPANDS! So be darn sure there is a properly functioning expansion tank directly connected to the water heater with no check valves in-between AND a T&P valve (Temperature and Pressure safety valve) installed on the water heater.

Then as water heats and expands, it has somewhere to go (expansion tank). And should the expansion tank malfunction or the water heater malfunction and heat the water too much, the T&P valve will release excess pressure and prevent an explosion.

[Bob F]

That kind of check valve needs gravity to be naturally closing the flapper to work properly at low flows. The flapper should be hanging down from it's hinge point if the valve is horizontal, or the flapper should be at the top if vertical, so it is always closed at no flow. The simplest solution for you might be to replace it with a spring check valve that doesn't depend on gravity.

[jeff_wisnia]

If the "initial stream" starts immediately when the faucets haven't been opened for an hour or so, then it probably isn't backflow, unless there isn't much distance between the heater and the faucets.

If it takes several seconds before hot water appears after opening a cold faucet then your presumption about the check valve may be correct.

Can you try telling what's going on by feeling the cold water piping on both sides of the check valve while someone else opens a cold faucet?

Jeff

[HeyBub]

Heh! My water pipes go through the attic.

Yesterday, the attic's temperature reached 134°F (even though it was a balmy

104° outside).

[Don Young]

In addition to the advice others have given, it may help to know that crossflow leakage when a single handle faucet is turned off is possible and can cause your symptoms.

Don Young

[SteveBell]

The initial slug of hot water is probably the water that's in the pipe in the wall. If it's an outside wall or the pipes run through the attic, that water can get pretty warm.

After the water in the wall runs through, it's followed by water that has been underground, or in the basement ceiling, or whatever depending on how your house is built. Eventually, you get to water that has _definitely_ been sitting underground.

[clare]

The water pipes in the house I lived in in Livingstone Zambia had the pipes on the outside, and the water mains were about 6" underground. Never turned the geyser on in the hot season, and the water from the COLD tap was hot enough to steam sometimes. British Colonial style system with float controlled gravity tank (like a stock watering trough) in the attic, gravity flow to the geyser and taps, so limited water pressure as well.

[Dan Listermann]

I did that and it gets hot right away. Are spring loaded check valves common in house plumbing?

[Bob F]

They are commonly available at stores, if that's any help. Some may not be suitable for hot water pipes.

[jeff_wisnia]

I'd say that "Warm Hand Luke" test pretty much proves that your original suspicions about the check valve not closing are correct.

The present valve may have worked when new, but might have gotten grotted up over time and won't close now, which could have nothing to do with its orientation.

I've always had good luck with Watts products.

Here's a data sheet on one of their series of spring loaded check valves:

One the right size should work slicker than snot to solve your problem.

After putting in a new check valve it wouldn't hurt to check the expansion tank to make sure it's still working as it should. With the present check valve "leaking" you wouldn't have noticed if the expansion tank got "full" or has a ruptured diaphragm.

Happy Landings,

Jeff