It rained and the tank level barely moved. The usual causes are small rains, a stuck first flush, clogged screens or a broken conveyance line. Here's how to find it.
You watched it rain, you checked the tank, and the level barely moved. Sometimes that's normal. More often something between the roof and the tank is sending water somewhere else. Work through these in order, starting with the simplest.
Each inch of rain on 1,000 square feet of roof yields a little over 600 gallons before losses. A quarter-inch shower on the same roof is about 150 gallons, and the first flush diverter keeps the dirtiest early runoff out of the tank, so a light rain may add almost nothing. Check what actually fell at your place before assuming a fault. Our rainfall monitor shows recent totals across the Hill Country.
Packed leaves in gutters or on screens make water overflow the gutter edge instead of running to the downspout. Cedar and live oak debris is the usual culprit. After a hard rain, walk the roofline and look for staining or splash marks below the gutters. That's where your water went.
The diverter should fill with the first runoff, seal, and then pass clean water to the tank. If its slow-drain outlet is clogged, it stays full from the last storm and does nothing. If the outlet is wide open, or the float or seal is missing or stuck, it can drain continuously and send much of a storm to the ground. Clean it out, check the seal, and make sure the drain is only dripping.
Most tanks have a basket or screen at the inlet. When it's full of debris, water backs up and spills over before it gets in. Clean it after the first big storm of each season.
If your downspouts feed an underground pipe that rises into the tank, that pipe stays full between storms. A cracked joint or root intrusion underground can lose water without any sign at the surface, and a blockage stops the system from filling at all. Signs include a soggy spot along the pipe route, or water standing high in the downspout risers during a storm while the tank stays flat. This one usually needs a pressure test or camera to find.
If the tank fills during a storm but drops afterward, look for a leak rather than a collection problem. Turn the pump off overnight and mark the level. If it still drops, the tank or a fitting is leaking. If it holds, something in the house or irrigation is using water. See what to check when a rainwater tank is leaking.
If the gutters, screens and first flush check out and the tank still isn't filling in real rain, the problem is usually in the conveyance line or the tank inlet. We diagnose and repair systems from any installer across Dripping Springs, Driftwood, Wimberley and the rest of the Hill Country. Call (512) 829-5800 or request service online. Our maintenance plans keep gutters, screens and the first flush on a schedule so this doesn't catch you in a dry spell.
Questions about your system? Call Dripping Rainwater at (512) 829-5800.
Request service
