BOOSTERS, BACKFLOW, AND LEGIONELLA SERIES
The majority of our troubleshooting revolves around suction problems. Anything that prevents water from getting to the water pressure booster pump system will affect the pumps. Here are some real world situations we come across routinely.
- Unattended strainers (backflow and meter)
- Filters
- Closed shut-off valves (yes, it happens)
- Air traps in piping
- Water softeners
- PEX piping
1) Unattended strainers (backflow and meter)
In addition to being a legionellae “harbor”, strainers get clogged, and cause critical pump suction problems.
One of our clients, a maintenance supervisor at a large hotel, lost his job because the XYZ hotel couldn’t rent out the top two floors, which cost them tens of thousands of dollars. In the end, the strainer was 95% clogged and the booster couldn’t get enough water. It was a cheap fix!
The blue strainer below is a perfect example of XYZ’s system. Isolating and cleaning the strainer will prove difficult, as there are no visible shut-offs upstream. We see this time and time again.
Below is an example of a smaller 1″ ball valve on the cover. The problem: opening the valve will NOT flush and clear the debris, as evidenced by the internal scale. Notice that the “coral reef” of scale is actually downstream of the strainer, which begs the question: how effective is the strainer?
Below, the brass “meter” strainer is located upstream of the meter, and often neglected. The water company should be responsible for cleaning this, so double check with them.
SOLUTION: Before installing strainers, consider the long term pro’s and con’s and associated costs (fouled backflow preventers, maintenance costs, extra isolation valves, etc.).
2) Filters
Whether a whole house “blue” filter, or a more robust commercial stainless steel filter, they get clogged over time, just like strainers.
SOLUTION: Filters are best installed after the booster pumps, and cleaned on a regular basis. If pressure gauges (on each side of the filter) are monitored, a high differential will indicate cleaning requirements.
3) Closed Shut-off Valves
The phone call was from another hotel, again: “every time we have high occupancy, the water pressure booster pump system crashes”.
To make a long, long story short, after hours troubleshooting the pumps, we got pictures of all of the piping and valves.
The pictured 4” shut-off valve is an OS&Y gate valve, and the center stem, when open, should be protruding at least 6” out from the valve’s wheel handle.
The valve is at least 90% closed, so there’s no water for high volumes! Opening the valve solved all the problems.
What really happened: the backflow tester failed to open the valve after completing the test.
SOLUTION: After maintenance, double check the system valves.
4) Air trapped in piping
This is a tricky one, because it’s not common, and it’s tough to identify! Whenever pipe goes up, across, and back down, there’s a good chance of getting air trapped. The bigger the pipe, the longer the distance, the bigger the potential problem. At low volumes, it’s not noticeable, but when the volume increases, the air will “block” the water flow.
SOLUTION: Be aware of elevated piping and “loops”. If questionable, install air-release valve(s) at the highest point(s).
5) Water Softeners
These should be installed after the booster pump, as it’s better to push the water through them than pull the water out (verify water softener IOM).
Problem 1: Undersized water softeners. “Let’s use the smaller, cheaper one” is not a good strategy when picking out a water softener. Verify the pressure loss at higher volumes.
Problem 2: Pressure rating of water softener may be too low for installation after pump.
SOLUTION: Have a professional size the water softener, and don’t be cheap! If it needs to be installed before the pumps, verify installation requirements with manufacturer. And verify pressure loss!
6) PEX piping
More of a residential water booster pump problem, but it is still an issue in commercial systems. And it will become a bigger problem as the PEX market expands!
Many PEX manufacturers use “insert fittings”, which have a small ID (inside diameter). What appears to be a 3/4” pipe/tube really has a 1/2” waterway. The friction loss is HIGH, and plays havoc on the volume of water and delivered pressure.
SOLUTION: Be cautious using PEX on the suction side of any pump. When using insert fittings, up-size the pipe for a “true” INSIDE DIAMETER.
Thank you for taking the time to read this article. Dennis (dennis@towle-whitney.com)