Hot Tub Repairs and Remodeling
PATCHING AND REPAIRING HOT TUB SURFACES
If your hot tub is gunite and plaster, you might need to be familiar with simple
patching techniques applicable to the walls. This section will also examine repairs to acrylic surfaces.
Plaster Hot Tub / Spa
RATING: ADVANCED
When the hot tub is drained for any reason, you have an opportunity to look for plaster blisters or pop-offs, areas
where the plaster has come away (delaminated) from the underlying surface. Such areas can be anything from the size of a quarter to dinner plates
to several square feet. Beyond that and you might need to replaster.
The causes of delamination, also called calcium bleed, are numerous. The original plaster job might have had poorly prepared surfaces,
poorly mixed materials, or too much drying before the water was
added. Most likely, however, improper water chemistry has created
aggressive water, stripping calcium from the plaster, weakening the
plaster layer and allowing it to separate from the underlying surface.
Some blemishes will be obvious, the plaster having cracked and
fallen away. Others will appear as discolored spots from the water that
has entered between the plaster and the subsurface. You can also look
for plaster faults by tapping suspected areas with the handle of a screw
driver or with a hammer to listen for hollow sounds (assuming the hot tub is empty). If you are committed to making repairs, poke around the
entire hot tub with a chisel or screwdriver to pop the blisters. They have to
come off anyway, so you might as well discover them all. Once you've
been around the entire hot tub, you can then evaluate if patching is the
answer or if replastering is more logical.
When you have identified blisters, chip the loose plaster away all
e cus- around the area until you reach solid, dry plaster. Use a hammer, chisel, or screwdriver depending on the size of the blister. Once it is completely exposed, clean the area of all water and loose debris. To make
sure the final patch blends in and appears even, clean up the jagged
edges of the blister area by sanding the perimeter. The most effective way
to smooth out these edges, especially if there are many blisters to repair,
rttling is to use a power grinder with a small [6-inch-diameter (15-centimeter)] hot tub. diamond grinding wheel. The objective is to create a clean, smooth edge
as can all around. You are now ready to patch.
The best way to learn how to work with any repair material is to practice in the workshop before attempting the repair in the field. A little
wasted material is less costly (in time and money) than making mistakes
on your hot tub. All these materials are available at your supply house.
Mixing a batch of plaster for patching (or practice) and the actual application are simple.
1. Water Start with a clean 5-gallon (19-liter) bucket, adding 4 cups (1
liter) of water.
2. Mixture Slowly stir in calcium chloride (the powder used to make the
mixture set up) until the liquid becomes warm to the touch. The
reaction of the calcium chloride will actually make the water heat up.
You will use less than 1 cup (250 milliliters), but keep monitoring the
temperature (the chemical will not harm your fingers). Too much
calcium chloride can actually melt plastic buckets, so don't be too
heavy-handed. The general rule of thumb is 1 part calcium chloride
for every 10 parts of cement used. You can also make patch material
without it for a slower-drying mixture. This might be helpful if the
area to be patched is not underwater and it is a hot, dry day (or a
windy day when the material will dry quickly anyway). Faster drying
means greater likelihood of cracking. Again, practice with several
mixtures and compare results so you become familiar with both the
art and the science of plaster patching.
3. Admix Add 8 cups (2 liters) of white cement and 4 cups (1 liter) of sand (the supply house will have a specially mixed grain size of sand called aggregate). Mix the materials thoroughly with your hands, adding water if needed to achieve the texture desired for the particular patch job.
TRICKS OF THE TRADE: PATCH MIXING
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An alternate method of mixing the patch material, which is especially useful if you are preparing a very dry mix for an underwater patch, is to first combine the dry materials in a bucket, then slowly add the water until the desired consistency is achieved. If you dry
mix, first put the sand in the bucket, then stir in the calcium chloride and cement (because these are lighter than the sand, they will combine more readily if they are
added to the sand, rather than the other way round). |
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For patching vertical surfaces, pool walls, for example, the mixture should be thicker than if patching a horizontal surface. The texture of bread dough will make the patch material adhere and stay in place better as it dries. The looser texture for horizontal surfaces gives greater flexibility and drying time when making the repair. |
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When patching underwater (which is most common), the texture should be as dry as you can make it and still work the material. Obviously, as you fill the patch area underwater, onthe material will pick up additional moisture and the texture will loosen. |
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The mixture created is called a 50/50 admix, even though there is twice as much cement as sand. That is so because the weight of the sand is one-half that of the cement, meaning the final mix is actually equal weights of each.
If the plaster in the pool or hot tub is colored, add the color powders
slowly and keep mixing until you reach the approximate shade
required. The most important consideration in creating patch mixture is to consider the drying time and conditions. If the plaster dries
too fast, it will shrink and crack. If the material is too thick, then it will not smooth out when you apply it and the result will be rough and unsightly. As noted previously, practice before going out to the job site.
The above recipe will make enough material to fill an 18-inch- diameter (45-centimeter) patch about 'A inch (13 millimeters) deep. Remember, once you start the job, it might not be practical to mix more material and if you do, it might not appear the same on the repaired area as the first batch. Therefore, always mix more than you need.
4. Patch Apply the patch with a trowel, using broad strokes, trying to fill the entire area on the first application. Try to fill so that the patch material is higher than the surrounding plaster level, then remove the excess by scraping the trowel edge across the surface, making the patch clean, smooth, and level. Actually the best finishing tool
for this smoothing is a straight piece of cardboard or plastic.
The other application method is underwater, where you work
by hand with a fist-size ball of material and push it into the patch area with your fingers. Again, use more than you need so you can scrape off the excess, feathering the edges into the existing plaster for a smooth finish.
One last plaster patching technique is used to fill small surface
cracks. Not all visible cracks allow water to penetrate the subsurface or cause delamination. Some are from too rapid drying or minor settling
of the surrounding land or the hot tub itself. If there are no blisters, patch
only the cracks.
The objective of patching small cracks is to slightly widen the crack so that it will accept patch material. You can use a small chisel to create a slight V shape along the crack. Follow the patching directions as out there lined previously, either troweling on the patch material or rubbing it eight of into the crack with your fingers and smoothing over the resulting repair with a straightedge.
Perhaps the most important aspect of any cosmetic patchwork is to
have realistic expectations. Even the finest patchwork will be visible for a few weeks, simply because the new material is clean and the existing plaster has darkened with age. Colored plaster takes time to mottle and blend.
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