Hawaii ranks #36 of 37 in the DrainDispatch Drain Risk Index, with a composite score of 18 out of 100 — among the gentler environments in the index. The median across all 37 states is 40.
What is driving the Hawaii score
The larger of the two contributors in Hawaii is water hardness.
Freeze depth: 0 inches (sub-score 0/100)
At roughly 0 inches, the Hawaii frost line is shallow and frozen laterals are rare. That removes one of the two common causes of joint movement, which means recurring blockages here are more often about grade, grease or root pressure than about winter.
Water hardness: 20-100 ppm (sub-score 16/100)
Supplies across Hawaii typically test 20-100 ppm — soft to moderately hard. Softer water means slower scale build-up, so the effective diameter of a sound pipe holds up better over decades than it does in hard-water states.
What this does and does not tell you
It describes an environment, not a property. A high score means buried drain lines in Hawaii face more pressure on average. It says nothing about your house. Pipe material, the age of the lateral, how it was originally laid, and whether there are mature trees over it all matter at least as much — and none of them is in this version of the index.
Version 1.0 uses two factors. Housing age, tree canopy and storm intensity are planned for 2.0. We would rather publish two factors we can source than five we cannot.
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DrainDispatch routes drain and sewer calls to independent licensed contractors across 42 Hawaii towns and 55 ZIP codes. Coverage is not statewide. See every covered Hawaii town →
States either side of Hawaii
Full index, all 37 states, with methodology →
Questions
What does a score of 18 mean for Hawaii?
It places Hawaii at #36 of 37 covered states for environmental pressure on buried drain lines — among the gentler environments in the index. It is a relative measure across states, not a prediction for any individual property.
How is the score calculated?
An unweighted mean of two normalised sub-scores: frost line depth (0 inches scores 0, 80 inches scores 100) and median municipal water hardness (20 ppm scores 0, 275 ppm scores 100). Hawaii scores 0 and 16 respectively.
Why unweighted?
Because we have no defensible basis for preferring one factor over the other. We would rather say that than invent a weighting that looks more scientific than it is.
Can I republish this?
Yes. The index is published under Creative Commons Attribution 4.0, so you are free to use, adapt and republish it, including commercially, with attribution to DrainDispatch.
Where does the data come from?
Published state frost-line depth reference tables and published state water-hardness data. Both are cited on the methodology page.
Does a high score mean my Hawaii drains will block?
No. It means the environment is harder on buried pipe on average. Housing age, pipe material and tree planting matter at least as much, and none of those is in version 1.0.