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Step 4. EXCAVATION
Correct excavation of the spa is very important. A hole that is too small can mean hours of picking and
shoveling by hand. A hole that is too large will require extra import material, which if not dealt with properly, can result
in settling or bulging of the spa.
The excavation should be dug very close to the spa size with a minimum disturbance to the unexcavated soil
which will support the spa. The clearance is approximately 6" on the sides and 6" on the ends (Fig 2).
The depth of the excavation is determined with the use of a transit level and a measuring stick. The bottom
of the excavation is over dug approximately 4". Spas will require approximately 2 to 5 yards of sand for
backfill (more may be required if the spa is over dug).
The excavation should be 6" larger than square from the desired elevation of the spa. It can be helpful to give
yourself extra room the first 6" in width and 12" in depth of the hole, to get past the coping, and allow space for the
skimmer and the main drain. Also, keep in mind that the wall of our spas are tapered, usually 1" in for every 12" in
depth. A place for the skimmer must also be dug in the side of the excavation wall. The skimmer cutout should be 2' by
2' and 3'
If dramatic over digging occurs in the bottom of the hole, never use excavated material to fill in the hole to the
desired depth. The material will settle. We suggest road base (a tamper may be needed) compacted thoroughly, and
topped with sand. If the sides of the hole are dramatically over dug, road base should be used beyond the six inches of
sand. Both should be compacted thoroughly during the backfill process. In the case of over excavation on the sides of
the spa in seasonal high water or poor drainage areas, you may want to mix 10% Portland cement to the backfill for
stabilization.
In areas that experience seasonal high water or experience considerable water seepage during excavation,
a permanent sump line (see Cross Section A-A) must be installed to alleviate the excess water and the associated
hydrostatic pressure accompanying it. Viking Spas suggests digging an 18" x 8' x 18" trench across the deep end of the
excavation. Six inches of 1 1/2" rock should be placed in the bottom of the trench. A joint of 3" perforated PVC pipe
is placed on the rock base and connected to a vertical stand of 8" PVC pipe running to the surface of the excavation.
The 8" PVC should be trimmed with a skimmer ring and lid for aesthetics and safety. After the connection has been
to the vertical stand of 8" PVC, finish covering the 3" perforated PVC pipe with 1 1/2" to 2" rock to the bottom of the
excavation (See Cross Section A-A). Cover the new sump line with fabric. The bottom of the excavation is now ready
for approximately 4" of sand bedding.
Figure 2
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