Keep condensate line filled with water?

[fiveolddogs]

A relative had a water heater installed a few years ago. As part of the install, a condensate line was formed into a loop, attached to the tank, and then terminated at a floor drain.

I was astonished to learn this week that the installer had instructed the homeowner to keep the condensate filled with water. She is not strong enough to squeeze the hose clamp to remove the hose and has been paying someone to come by and manually detach the hose, fill it with water, and put it back in place every few weeks.

Clearly the loop of hose is meant to act as a trap, but since it is not plumbed into the sewer line, is there any reason to do this?

 

[fiveolddogs]

I'll bump this in hopes of a reply.

 

[Sponsor]

 

[Bannerman]

Natural gas exhaust often contains sufficient moisture which may condense on the inside of the cool plastic exhaust piping. The drain line will allow any resulting condensation to drain away so it will not accumulate in the system.

The WH power vent fan will cause the combustion exhaust gases to be somewhat pressurized to blow the gases out to the exterior through the plastic pipe. The water that is to remain within the loop will prevent the exhaust gases from being blown into the home's interior through the drain tube.

The photos show insufficient water currently in the loop as the loop should be full so any additional condensation will cause the loop to overflow and trickle to the floor drain while the remaining water will continue to prevent exhaust gases from passing through.

Any condensation that does form in the exhaust piping will only add to the water already in the loop so adding water every few weeks should be unnecessary.

If the home's heating system is routinely serviced each year, replacing the water to prevent mold in the WH loop is often added to that annual procedure at minimal cost.

 

[fiveolddogs]

You say:
The water that is to remain within the loop will prevent the exhaust gases from being blown into the home's interior through the drain tube.
and
Any condensation that does form in the exhaust piping will only add to the water already in the loop so adding water every few weeks should be unnecessary.

But what happens is the system does not produce enough condensation to keep the tube loop full of water. Over the time of a few weeks, the water evaporates and the loop becomes empty, like in the pictures.

So the primary question is: if the tube loop becomes empty, is it important to manually fill it back up?

An additional question based on your previous reply is: is it unusual that the loop should be drying out the way it does every few weeks, and if so, does it suggest a potential problem with the exhaust system?

 

[Reach4]

Things seem surprising to me. If I went with this, I would make the loop a lot taller. I am thinking of increasing 4 inch diameter to 10 or 12 inch diameter. That would hold more water, and withstand more pressure.

Does the WH maker call for this?

 

[Bannerman]

Since no air/exhaust gases should be passing through the drain tubing, the water within the loop should only evaporate very slowly as the only exposure to air is that within the cross section of the tubing.

That size loop should contain a sufficient quantity of water so I would expect it should not evaporate for at least several months.

If you were to fill the loop to where it begins to overflow, once reconnected and the WH fan is operated, how much water will exit the loop? While there will be a small quantity expected to drain, the amount should not be substantial. If a substantial quantity of water is pushed out, then there is likely a blockage in the exhaust vent piping or the fan is moving too much air and will require adjustment.

With regard to the importance of water within the loop, exhaust gases (potential carbon monoxide) entering the home is to be prevented for the health and safety of the home's occupants.

 

[fiveolddogs]

I really appreciate the comments and information.

I am having trouble reconciling two statements in your last reply:
Since no air/exhaust gases should be passing through the drain tubing, the water within the loop should only evaporate very slowly
and
With regard to the importance of water within the loop, exhaust gases (potential carbon monoxide) entering the home is to be prevented for the health and safety of the home's occupants

These statements seem somewhat contradictory. Is the water in the drain loop required to prevent exhaust gases from entering the home? Is it necessary to create this drain loop when installing the water heater? I have seen installation instructions that do not include this.

 

[Bannerman]

Is the water in the drain loop required to prevent exhaust gases from entering the home? Is it necessary to create this drain loop when installing the water heater?

Yes, for the reason stated in para 2 in post #3.

I have seen installation instructions that do not include this.

I suspect those manuals relate to WH models that are not power vented with a fan but instead rely on convection to exhaust through a 'B' vent or chimney. The exhaust for appliances vented by convection will be hotter. When the exhaust gases remain hotter, the additional heat will cause the chimney to also become warm thereby reducing the likelihood for moisture to condense on the chimney walls.

A function of the power vent fan is not only to push the exhaust gases through the 2" plastic vent pipe, but also to dilute the hot gases with a large volume of cooler air so the exhaust temp will not exceed the temperature rating for the plastic vent pipe.

Have you attempted to fill the loop and then run the power vent fan to see how much water is pushed out from the loop?

 

[Reach4]

Have you attempted to fill the loop and then run the power vent fan to see how much water is pushed out from the loop?

Another related measure is how the level of the water on the left differs from the water on the right.