By Matthew Baring-Gould, Kingscliff-based drainage plumber. Servicing Tweed Heads for 4 years. 5.0 stars across 173 Google reviews. Licensed NSW 383340C and QLD 15036450. ABN 74 605 392 348.
Bundall riverfront property. The previous plumber had run the entire house stormwater system into a 50mm PVC pipe and then into a short piece of 50mm aggie pipe discharging at the wharf. Completely undersized. Cleared what we could and gave the owner a written explanation of what the right system looks like.
What the customer called us for
Bundall riverfront owner called us out because the stormwater outlet at the wharf was constantly surging and backing up during rain.
What we found when we got there
The entire house stormwater had been plumbed into 50mm PVC. From the house wall out to the river wharf, the line stayed 50mm, then converted to 50mm aggie pipe for the final metre to the water. For a full house of catchment, the right diameter is 100mm minimum, usually 150mm.
Why we did it this way
The customer already had an existing plumber who had designed the system. They were not asking us to redesign it — they were asking us to clear the line so it drained again. We did that, and we also gave the owner the honest technical answer in writing so they have the information when they go back to their original plumber.
What we did on site
- Hydrojetted the full 50mm stormwater run from the house out to the wharf.
- Pressure-tested the aggie pipe outlet.
- Confirmed flow was restored for the current rain profile.
- Walked the owner through what a correctly sized stormwater system looks like for a residential catchment of that size.
- Issued a written note documenting the pipe diameter and the recommendation.
The result
Line draining again. Owner now has clear documentation that the system is undersized, which they can take back to their original plumber or use when they next upgrade the property.
If you have the same issue
If your stormwater outlet is permanently surging during moderate rain, the problem is almost always undersized pipe diameter, not a blockage. A camera can confirm the diameter in minutes. The fix is a proper upgrade to 100mm or 150mm. Call Matty on 0447 188 394 or request a quote.
Customer names and addresses have been withheld. Individual results vary. Drain Masters Plumbing is licensed in NSW (383340C) and QLD (15036450).
Frequently asked
What size stormwater pipe should a residential house run on?
Minimum 100mm from the downpipes to the discharge point. For properties with lots of hard-surface catchment (big driveways, big patios) 150mm is better. 50mm is only ever used for internal fixture branches, never for a main stormwater run.
Why would any plumber install 50mm for a whole house?
Usually a low-budget install where the plumber used whatever stock they had on hand. It will drain in dry weather and most of the inspection cycle. It only fails when real rain arrives.
Can you just add more 50mm lines instead of upgrading?
No. Flow capacity does not scale that way. The correct answer is to replace the main run with properly sized pipe.
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