Frequently Asked Questions about Mainline Backwater Valves
Q: Are Mainline Backwater Valves available in different sizes and materials?
A: At this point in time, they are only produced in 4" ("Schedule 40" ABS and PVC.) We urging the factory for a 6" backwater valve, but liability and engineering issues seem to be in the way.
Q: What is Difference between PVC and ABS?
A: These are two different chemical formulations of plastic commonly used in Drain, Waste and Vent (DWV) systems and are joined by solvent cementing. PVC stands for PolyVinyl Chloride and ABS stands forAcrylonitrile-Butadiene-Styrene. Different solvent cement is required depending upon the type of pipe being used.
Q: Should I use ABS of PVC?
A: First, your local plumbing code governs which material must be used in your area, but it is also important to know that you should not ever mix the 2 materials as the solvent may not bond them together properly.
Q: How do I adapt to Clay or Cast Iron pipe.
A: A company called Fernco makes a wide variety of Neoprene Rubber Adapters that clamp to the outside diameter of the pipe and the backwater valve with stainless steel clamps and sleeves. We do not supply these adapters as various plumbing codes require different Fernco models which can easily be purchase at your local home-center or plumbing supply.
Q: Can I increase from 3" pipe to a 4" Backwater Valve or Adapt-A-Valve?
A: From a mechanical perspective, you may increase from 3" to 4" on the INLET (uphill) side of the valve with a concentric or eccentric reducer, but must only use an eccentric reducer on the OUTLET (downhill) side. Reducing on the outlet side with a concentric adapter would cause the bottom of the smaller diameter 3" pipe to be higher than the bottom of the valve, causing the gate to be submerged with reduced flow over it's surface. With a reduction in the self-cleaning flow, sediment would build up and thwart the gates' ability to close. You must also check your local plumbing code to be sure that using a reducing adapter is permissible.
Q:Why do both ABS (Black in color) and PVC (White in color) Mainline Backwater Valves bear an "ABS" stamped right into the material on the bottom of each valve?
A: Mainline currently has only one mold, and it was stamped ABS because that was the only material they produced when the company began production. Molds are incredibly expensive and the same mold is used for both ABS and PVC, now that PVC valves are being produced.
Q: I live in a city that routinely flushes out its sewers with highly pressurized water. Do you have any experience with the normally open Backwater Valve in a flushing environment. Will it close in time so as to prevent damage?
A: Most municipal sewers are flushed with high pressure on a fairly regular basis. The Fullport Backwater Valve and Adapt-A-Valve should both work if installed properly and maintained (check that the gate moves freely) on a regular basis. The combination of air and water will close the gate.
Q: How much slope is required in a drain line in order to use a backwater valve?
A: In all installations, make sure the slope is adequate. It must be at least 2% (or 1/4" per foot) to insure proper operation.
Q: What is the "Laminar Flow Rule?"
A: Laminar flow is a term described the smooth movement of a fluid through a pipe. Openings in a pipe interrupt this smooth flow. The "Laminar Flow Rule" states that no branch lines should be taken off within 2' of the backwater valve to insure laminar flow across the gate of the valve. This aids the self-cleaning process as the flow moves across the gate and insures the gate is not constantly moving up and down in the midst of turbulent flow.
Q: What is the leakage rate of the normally open backwater valve?
A: The allowable leakage rate up to 2ft head is 1 Liter per 10 minutes, as head pressure increases over 2ft there is no leakage.
Q: How much pressure can a Fullport Backwater Valve or Adapt-A-Valve withstand??
A: The gates are designed to withstand at least 50psi, the weight of a 100 foot column of standing water which is ample in just about all imaginable residential applications.
Q: What is the Mainline Fullport Backwater Valve and Adapta-A-Valve warranty?
A: Mainline Backwater Valves and Adapta-A-Valves are warranted by the manufacturer for 1 year against manufacturer's defects. The actual installation of the valves can not be warranted by Mainline.
Q: Can the Adapt-A-Valve Test Gate be used in an emergency to shut off back-flow?
A: Yes. The Test-Eze Gate can be used as both a Test Gate and as an Isolation or Knife Valve.
Q: With a Normally Open Gate Valve, what is the chance of the valve not closing?
A: As long as the valve has been properly installed (proper slope, laminar flow rule followed) and is clean and maintained, it will close.
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Phone Greg at 330.836.9393
