Why a failing preventer goes unnoticed
The assembly sits there doing nothing visible whether it is sealing or not. A check valve with a weak spring or a worn seat looks identical to a good one from the outside. That is why we treat the test as the real diagnosis. If you don't know when your assembly was last tested, or you are unsure it ever was, call and we will put gauges on it.
How we test it
Inside the assembly are two check valves, and each one has to hold against reverse flow. We connect a differential-pressure gauge to the test cocks on the assembly with hoses, then bleed the air out of the tester and the hoses so the reading is accurate. Air left in the lines gives a false result.
With the gauge set up, we test each check valve for tightness against reverse flow. While the test runs, we also confirm that the shutoff valves hold. A shutoff that leaks can spoil the test or let water past when it shouldn't, so we check it every time instead of assuming it is fine.
What we repair when it fails
If a check valve doesn't hold, we open the assembly and look at what is worn. The parts we carry for this are a relief-valve service kit and check-valve springs. A tired spring is a common reason a check lets go, and replacing it is much cheaper than replacing the whole assembly. Because the relief valve is already open on the bench, we service it with the kit at the same time.
If the shutoff valves are the problem, we tell you what we found before we do anything. If an assembly needs parts we don't have on the truck, we say so before we leave and set a return visit.
What it costs
Testing a backflow preventer runs $30 to $300 per device. We can give you a typical range on the call. The exact number is confirmed once we see the assembly and what shape it is in. The price is per device, so a property with more than one assembly is figured per assembly. If the test shows a repair is needed, we quote that before we start, so you decide with the number in front of you.
Permits in Denton
If what you are asking for goes beyond testing and servicing the assembly and changes the system itself, we sort out the permit question with you before any work starts.
Typical Denton Pricing
These ranges show roughly what this work costs, and the final price goes in writing before anything starts.
$75–$250
Related Services
Our Process
Concretely, it looks like this:
- Open the test cocks individually to flush out sediment, then close them.
A two-minute call is all it takes, and it costs nothing to ask.