How to Install an Overflow Water Tank Valve

When it comes to a do-it-yourself project, the level of complexity of the project and confidence in your ability to take on said project could determine success. For instance, take having to install a drain valve in the overflow water tank of a hot water boiler system.

I recently purchased an old row house in need of much renovation. It is livable. But, that is only because I choose to live in it. Winter was approaching and I needed to verify that the boiler was working. So, naturally I called the local utility company to come out and service it. The repairman came out, took a look at the boiler and said he could not activate it until I replaced the drain plug in the overflow tank with a drain valve, and that he would happily charge me $239.00 to replace it. I immediately accepted his estimate, thanked him for coming out and helped him to the door. I said to myself, "$239.00, I'm going to have to think about that one."

A couple of days later I went to the home improvement store. While shopping in the plumbing section, I found the drain valve the repairman required for activating my boiler system. It cost less than $6.00! He was going to charge me $239.00 to install a valve that cost less than $6.00. There is no way, "I thought", that I'm paying that kind of money to install a $6.00 valve! So, I went home to face my next do-it-yourself project.

I am not a novice do-it-yourselfer. However, I have never worked on a boiler style furnace. In fact, I have never attempted more than a simple filter replacement on any furnace. But, I was not going to pay such a high price for a simple valve installation. So, here are the steps I took to install the valve.

First, you must understand that a hot water home heating system is a closed and pressurized system. The purpose of the overflow water tank is to relieve pressure on the system. Consequently, it fills with water, and is under pressure. I began by putting a large bucket under the tank and slowly opened the drain plug, letting water drip from the tank.

I estimated that the tank was at least half full, and at fifteen gallons, it would take several hours to slowly drain it. This is definitely a weekend project. You must periodically monitor the bucket to prevent it from overflowing. It is a good idea to have a secondary bucket near by, which you can use to temporarily catch water while you are emptying out the primary one.

After emptying out 3 buckets of water (at about 5 gallons each) I anxiously opened the drain a little more, letting water drain out a bit faster. After emptying 2 more buckets, I decided to open the drain completely and let the remaining pints of water drain out. I got the valve, put a ladder under the tank, climbed up and removed the plug. And to my surprise, I opened the floodgates and water gushed out! It is clear to me now that I under estimated the amount of water in the tank, or in the bucket, or both! Actually, the additional water was probably from the rest of the heating system on the 2 upper floors of the house.

Frantically, I grabbed the valve, stuck it in the hole and began threading it in. Lucky for me that I wrapped the valve's threads with Teflon thread sealing tape before I removed the plug. With my face dripping with bilgy water, I securely tightened the valve, then stepped off the ladder to dry my face and wipe the taste from my mouth (it was nasty).

Once the valve was successfully installed I attached a garden hose to it and drained the remaining water from the tank. With the tank and the rest of the system completely drained I was now ready to refill the heating system with fresh water in order to heat the house for the winter. Afterward, I reflected on my success and the price I paid for doing it myself:

1. One drain valve - $6.00.
2. One mouth full of bilgy water - unpleasant, distasteful but tolerable.
3. Not having to pay a greedy utility repairman $239.00, priceless.

So, hopefully these steps will help you save some money. To avoid the taste of nasty water, be patient and let the tank drain slowly, but completely.