To make a single balloon arch, first construct a base to support the arch using umbrella stands, buckets or wood blocks. Depending on the height needed for the arch, glue sections of 1/2-inch, 10- or 20-foot PVC pipe using PVC connects and PVC cement. Insert the PVC into the bases and allow the glue to dry. Begin attaching the balloons by tying balloon clusters around the PVC.
To use an umbrella stand base, remove the umbrella poles in two stands and insert the completed PVC pipe arch. When using buckets, take two large pails with lids and create a 3/4-inch hole in the center of the lids. Pour sand or rocks about halfway into each bucket, and then insert the pipe arch. When using wood blocks, drill a 1/2-inch hole in the middle of each of two 4-by-4-by-10-inch blocks. Use sandbags to steady the base, and glue the PVC pipe into the holes.
Place the arch where it is to stand for the event before adding the balloons. Use larger balloons to reduce the number needed to complete the arch. Ties two balloon ends together, and then another two before tying the two sets together to create a group of four balloons. Twist two of the balloons around the pipe to attach the group to the arch. Repeat across the entire arch until no pipe shows.