Hi,
We have a question, when shopping around for our new tub cover, we noticed that some manufactures use a mesh rather than a vinyl bottom. Which one is better and which one would you suggest?
Thank you,
Bruce and Elaine,
New York
Greeting Bruce and Elaine,
The Pros are glad to explain the philosophies behind each of these different types of under liners. The purpose of the under liner is to complete the “pillow case” pocket of the otherwise vinyl skin that encloses the foam cores.
The life of the under liner is almost harder than the life of the top vinyl that is exposed to the elements 24 X 7 X 365. The under liner lives in a dark, 100% humidity, chlorinated (typically) environment. Over the long term, the chemicals will eat through the vapor barrier, causing the cover cores to water log and fail.
What is happening under the cover when it is closed is the steam hits the cover, which is cooler than the steam, and condenses back into water. The under liner on a hot tub cover must allow this condensation to drip back down into the spa water, where the chemicals can again kill any bacteria, etc.
A solid material under liner, while it cannot keep the steam from pepenetrating, must be able to allow the inevitable condensation to escape. Solid under liners have weep holes put into the material. Some times the weep hole is a simple hole in the liner, and some times the hole will be finished with a grommet to give it more strength.
The Pros do not favor the solid under liner approach. In order for the condensation to escape, enough water must collect to then pull the liner down, so it can then run to and out of the weep hole. This technique insures that water, and relative large amounts of it, will be inside the cover at all times. The weep holes can also become blocked, further increasing water inside the cover. All of this can be unhealthy as this warm, moist and dark environment, free from the chlorine in the hot tub, can foster bacterial growth.
The same reasons The Pros do not favor a solid under liner are the reasons The Pros do favor the mesh bottom. With the mesh, the same processes of condensation occur, but only a single drop of water must collect before it can drip back down to the water. There is no need for water to collect, pool and run toward a weep hole. Also, the mesh can stay tight to the foam of the cover, with no need to channel water.
There is also an aesthetic answer to this question, as some like one look better than another, but The Pros do not need to weigh in on this and create any unnecessary controversy.
Happy Tubbing!
Ethel Elliott
