Aquasense | Sprinkler, Plumbing, & Electrical Contracting

Deciphering Test Results

After we have tested your assembly a part of our service includes sending a copy of your test report to your water district. All cities accept my easy to read computer-generated form except for the City of Kirkland, which we send a hand written copy to. An interesting by-product of computerizing my backflow program is the failure rate percentage of the different assemblies. Below is data compiled from 2004 through 2005.

Brand	Model	Quantity Tested	Failures	Failure %	Replaced	Type
Buckner	24101	6	2	33.33%	0	1
Conbraco	40-105-02	23	0	0%	0	1
	40-105-A2	70	6	8.57%	0	1
	40-105-A2T	13	1	7.69%	0	1
Febco	850Y	520	110	21.15%	1	1
	850	266	40	15.04%	0	2
Rainbird	DC-100 **	64	4	6.25%	1	2
Watts	709	264	85	32.20%	22	2
	007M1QT	191	10	5.24%	0	2
	007M2QT	8	2	25.00%	1	2
	775QT	36	4	11.11%	0	2
Wilkins	550	74	6	8.11%	1	1
	950DC	144	22	15.28%	0	1
	950XL	191	30	15.71%	1	1
	950XLT	664	64	9.64%	0	1
Totals		2528	384	15.19%	1.07%
** Note Rainbird DC-100 & Watts DC-709 are the same unit.

SAMPLE Aquasense Backflow Test Form

The above data is for landscape sprinkler assemblies only. Test results for double check valve assemblies usually range from 0 to 4.0 and 1.0 or higher is considered passing. I have divided the assemblies into type 1 and type 2’s. Type 1’s have check assembly parts that are easy to remove and clean, type 1’s will almost always pass after a failure. Type 1’s are the least expensive to maintain. Type 2’s have factory manufactured plastic check assemblies which may need replacing if they fail. The factory manufactured plastic check assemblies cost anywhere from $18.00 to $88.50 per check, making type 2’s more expensive to maintain. Within this group is the Watts 709 and the Rainbird DC-100 which are actually the same assembly made by Watts. The checks on this type of assembly are accessed by removing 4 flat head screws. Unless the assembly is in a large sprinkler box it is very difficult and sometimes impossible to access the checks without digging up the entire unit. In addition to the difficulty of accessing the checks, replacement checks are expensive. If this type of assembly fails and we are unable to repair it without excavation, we recommend replacing it with a Wilkins 950 XLT which runs on average $250.00 - $350.00 parts and labor installed depending on the location. Check your test results to see which type of assembly you have.

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