About the House: If the Shower Scalds With Each Flush By MATT CANTOR

Friday December 30, 2005

A man showers happily. He is singing to himself. Not bellowing, but really singing. It’s a torch song … no, it’s Donovan. “Mellow Yellow” I think. He’s smiling. He’s soapy. Suddenly a shadow falls across the shower curtain, a figure looms, then a sound, Ahh … Ahh … Ahh … He screams, backing away ... He screams, scalded by the remaining 125-degree water.  


Is this you, my friend? Do you suffer from the desperate plague of those consigned to “old pipe syndrome”? Well, dear reader, there is hope for you. You need not toil in fear any longer. Your marriage can be spared the threat of divorce over the innocent act of draining the bowl, and children need not fear for their allowances. A few minutes with your kindly plumber (twinkling sound) and you can be scorch-free. 

Welcome to the world of galvanized piping. To many of you, this is the real deal. Not all houses with galvanized pipe have this problem, but many do. Let’s take a slightly less silly look at the above problem. When flow through a piping system is impeded, the flushing of a toilet steals both pressure and cold water. This drops flow and also changes the balance of hot and cold pressures for a short while, resulting in the showering party getting more hot than cold. It can also result in such a loss of pressure that the shower, for all practical purposes, stops flowing. While not the norm, many older houses have this unpleasant condition, and for those who live in those houses (and you know who you are), it’s no fun. This is, of course, not dangerous, and the new homebuyer who figures this out may not prioritize such repairs, placing them in line behind foundation upgrade, seismic retrofitting and a new roof. But it is something that is very worth fixing. It will make life more pleasant and it will surely raise the value of the house.  

Depending on a few factors, this need not be a very complex problem to address. But there are a few things to find out and some notions that you may want to consider prior to hiring a plumber.  

If you’re lucky, you have most or all of your plumbing on one floor with an accessible crawlspace or a basement (best of all) below. If this is the case, the majority of the guilty piping is easily reached and therefore easily replaced. That’s right, we’re going to replace it. Yes, there are methods for flushing out old piping, but I would urge you to choose replacement instead. The primary reason is that flushing systems still leave you with relatively small pipe interior diameters as well as piping that has a lot of friction and piping that’s destined to corrode internally again.  

Unlike copper, galvanized piping rusts. It also grabs minerals and holds them internally, gradually becoming encrusted until it looks like the inside of a cave. In fact, if you cut out a foot-long section of old corroded “galvy,” you probably won’t be able to see from one end to the other, even though there may be a quarter-inch opening at either end, since this passage will not be uniform and the water has to find its way through the twists and turns created by the uneven build-up. This is part of why water flows so poorly through old galvanized pipe.  

Also, older houses are usually piped in 1/2” galvanized with 3/4” being used only for the main trunks on houses from the ‘40s or later. If your entire house is piped in 1/2”, that’s at least a part of your problem. Your plumber will probably want to re-pipe using 3/4” for at least the main trunk or manifold lines and 1/2” for the final branches only. These will be the lines that lead to the sink, the toilet and so forth. 

If you’re trying to make the pennies squeak, here’s a strategy you might employ. Try replacing only those lines you can reach in your basement or subfloor area (crawlspace). I also suggest you replace as much of the main as you can easily reach. If you do these portions, you might find that things are good enough to live with for quite a while. If you do this, it’s very important to keep your new copper (the only kind of piping I recommend for water systems) separated from the old galvy by use of some sort of “di-electric union.”  

Here’s the problem: If you take a piece of steel and a piece of copper and connect them and stick the opposing ends of each into water or into the ground, you’ll make a battery. This means that one of the metals is going to become a “sacrificial anode” and that anode is the steel. The battery gradually takes the steel apart one molecule at a time. Inside your pipes, this also means that those stolen ions leave sites where minerals bond, and so you have both destruction of the original pipe and the arteriole sclerosis that makes your plumbing exasperating. 

Here’s how this gets remedied in this “partial” upgrade: Having removed all the galvanized that can easily be reached, a long nipple of brass is inserted into a female fitting of galvanized (a brass coupling is even better). I suggest that at least six inches of brass be used at each contact point. This will inhibit the di-electric effect and protect the old galvized portions which remain. Copper can then be “sweat” or soldered together to replace the missing piping. Remember to use at least 3/4” for all major lines that serve multiple functions. The line to a single fixture can be 1/2” if it’s not extremely long. You can also simplify your piping system at this time. Many old system are unnecessarily circuitous or poorly routed. 

This is also a great time to add the oft-missing main water valve at the front of the house. It’s best if it’s on the outside at a spot that is easy to find and operate. On many older houses these valves are missing or located in places that are hard to reach, and installation of one can help minimize the effects of a gushing leak by making it easy to get to and use. 

While you’re there, you may want to add a pressure-reducing valve. This might sound silly given what we’re trying to achieve, but high pressure increases the likelihood of a damaging flood, even when water flow seems poor. Have your plumber test your line pressure (this is a function of the utility company’s equipment and you have no control over it, except to reduce it on your own home). If the pressure is high (80 is the upper threshold but anything over 100 is getting serious), adding a pressure reducing valve is a great idea and doesn’t cost much (the part is about $100-$150). 

And remember, in the mean time, it really isn’t funny flushing the toilet while your wife is in the shower.