One of the most important accessories that a storage tank can be equipped with is a pressure vacuum, frost proof vent.
Think of the vents as a kind of insurance policy. Sure, routine maintenance and inspections should be performed regularly and in accordance with state and federal standards, but pressure vacuum, frost proof vents help keep tanks damage-free and operable. Improperly vented tanks can cause external pressure on the tank. Buckling can occur, even at a low-pressure differential, according to AWWA D-100; 5.5 vents.
Whether your tank is in a cold-weather climate or a warm-weather climate, pressure vacuum, frost proof vents are necessary accessories. Ice or snow buildup around a normal vent doesn’t allow enough air to pass in and out. A pressure vacuum, frost proof vent has a breakaway mechanism that either has a pressure pallet or is spring-loaded. The pressure pallet will raise with the rising pressure, allowing air to travel in or out. The spring-loaded vent opens up and doesn’t freeze.
Live in a consistently warm or humid climate and not convinced that a pressure vacuum, frost proof vent is worth the expense? They do more than just prevent frost from freezing the tank. The vents also help stop birds and insects from building nests that clog the tank. Plus, installing a pressure vacuum, frost proof vent is required based on AWWA D100-11 recommendations.
“Tanks equipped with roofs shall have a vent above the top capacity level, which shall have a capacity to pass air so that at the maximum flow rate of water, either entering or leaving the tank, excessive pressure will not be developed,” according to AWWA D100-11.
A vent should always be located near the roof’s center, even if more than one vent is required. It should be designed to keep birds and other animals out. A pressure-vacuum or a separate-vacuum relief mechanism should also be made available in case the screen frosts over or becomes clogged.
Ventilation is important for tanks – whether they are ground or elevated. Vents helped allow for proper ventilation that’s lacking in other kinds of openings. Both manways and overflows are examples of openings in tanks. Neither are included in a tank’s design for airflow. So, if a tank needs to be sealed off, manways and overflows aren’t designed to allow enough air for the tank to breathe. A sealed-up vent can pull the vacuum on the tank, which can damage and even destroy the structure.
Installing a pressure vacuum, frost proof vent helps save money in the long run because frozen vents can be costly. A few years ago, at a Pennsylvania prison, a frozen vent caused a tank’s roof to cave in. Water pooled knee-deep on the roof after the cave in. It cost $500,000 to repair the damage.
Municipalities often paint the name of their towns on their water tanks. It’s a form of marketing for their community – letting passerby know which town they are visiting or driving through. If the tank is dented or marred near the name of the town – it’s very noticeable. As was the case for a town that’s elevated tank suffered a dent because the tank had frozen due to lack of water circulation. When this happened, the operator attempted to pull the water back out. The tank’s vent was so frozen that no air could be released. The tank overpressurized, leading to a dent right where the town’s name was emblazoned.
Older riveted tanks don’t typically have vents. Instead, they are equipped with finial balls that don’t allow for much if any ventilation. Finial balls should be replaced with vents when maintenance or repair work is completed on a tank if it’s remaining in service, according to AWWA Manual 42.
Pressure vacuum, frost proof vents are an important accessory for any type of tank – old or new, elevated or ground. Talk to one of our sales agents at Pittsburg Tank Maintenance if you want to learn more about vacuum pressure, frost proof vents.