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How To Diagnose And replace A Faulty Flo Check Valve

By Edited Jun 1, 2015 1 0

Multiple Flo Checks In A Hot Water Heating System

How To Diagnose And replace A Faulty Flo Check Valve, is an article that may save the average homeowner quite a bit of money if they can avoid a service call from a heating repairman. The rates that are charged for any heating repairs can vary from 70 to 150 dollars per hour, depending on your location and the reputation of the company. Better rep. usually means more demand which will mean a higher price per hour.

About The Hot Water Flo Check Valve

There are two basic types of flow checks that are commonly found in use with a multi zone hot water heating system. Both of these valves perform the same function, stopping the gravitational heat rise that normally occurs when water is heated within a boiler.

Without a flow check in each zone feed, the water in the boiler would naturally begin to rise up the pipe and toward the radiation in all zones whenever any one zone called. This is just a principle of basic physics as heat rises.

As the heated water begins to rise, it will push the cold water back to the boiler where it is reheated and this action continues and creates a circulation in zones that should not be getting heat. In other words the zones that are satisfied will get over heated because of the gravity flow.

When there is a call for heat from one thermostat in a multi zone system the boiler fires and the pump for that zone begins to circulate water through the piping and radiation for that zone. The remaining zones that are not calling will not circulate because they have a flo check valve in line that is preventing the gravity circulation from occurring.

When this valve fails, it is usually because it has become stuck open. Unbridled heat will flow. Basically the extra heat when you don't want it is the main symptom that will alert you to this condition.

Flo checks also work on the theory of gravity. There is a weight inside the valve that is just heavy enough to remain closed while boiler water is being heated. They actually operate when a pump on the other side pulls them open.

Gravity flow doesn't have enough push to lift the weight inside, but the pump sucks it open with little effort. When the zone is satisfied the pump shuts off and the weight inside the flow check valve falls and blocks gravity circulation from occurring.

Types Of Flo Checks

Brass Solder Type Flo Check Valve
The first type of flow check and the most common will be a sweat type or solder type that is actually soldered into the piping system. This valve can be rebuilt with replacement parts.

Unsoldering the body is seldom necessary. Replacement parts are available at most plumbing supply houses, as well as some of the larger building supply and home improvement outlets.

There are also on line venues like Amazon.com who will send the parts right to your house. Make sure to get the name of the flo check brand from the exact one you have as several different manufacturers are out there.

Cast Iron flo check
The second type of flo check valve is made from cast iron and will be wound onto pipe threads. Coming through with two female openings to wind them onto a pipe or you may have copper adapters wound into your flo check to adapt to copper pipe.

Either way these valves work in exactly the same way as the previous models except they are made from cast iron and are threaded on instead of soldering.

Repairing Your Flo Check

In order to make any repairs on the flo check valves in your heating system, an isolation valve must be located on each side of the valve to separate it from the rest of the system. If these valves are not present you may have to shut down the feed to the entire boiler. This should be a half inch copper line that ties into the city water main or your well pump.

After getting the water shut off or isolating the valve we must repair, take a pair of plumbers channel locks and remove the bonnet nut on the top of the valve. This will come up slowly and the knob on top should be turned along with the nut. After the nuts threads are completely out of the valve body, the whole assembly can be removed by pulling straight up.

If possible, inspect the cavity that the stem came out of. remove any small pieces of Debris or scale as best you can and then insert the replacement stem into the cavity. Install some pipe sealant compound on the threads and reinstall the retainer nut, making sure that you don't jam the assembly. Loosen the knob on top as you go if needed, so the valve doesn't jam it down as you tighten the retainer nut.

Restarting The System

Once this assembly is all back together you can open any valves you closed and turn the water back on. The job is complete and your gravity feed problems as well as any overheating will be solved.

Some systems will need to have the air purged out, if a lot was introduced. This is accomplished by pushing water through the piping with city water pressure or well pump pressure, depending on which one your house is using.

How To Diagnose And replace A Faulty Flo Check Valve, has hopefully enlightened you to the application of this valve and a way to repair them. Saving money is never a bad thing and maintaining your hot water heating system should always be a main priority.

Taco 219-4 3/4" Sweat, Bronze Horizontal Flo-Check Valve
Amazon Price: $62.22 $38.51 Buy Now
(price as of Jun 1, 2015)
Watts 0590715 1/8" FV-4M1 Automatic Float Vent
Amazon Price: $10.79 $6.23 Buy Now
(price as of Jun 1, 2015)


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