Excerpts from recent Houseboat forum exchanges at www.houseboatmagazine.com/forum:

dalehollow: In the Kentucky/Tennessee area we have water that freezes anywhere from 1 to 2 inches under our houseboat. Some of the standpipes in these hulls froze one time. 
Is it likely the weld in the standpipe could have been compromised or weakened? With the normal vibrations and wear-and-tear, do you think it can be compromised enough to cause concern?

easttnboater: How did the water freeze under your houseboat? I can see it freezing around the boat, but not under it. 
If the welds were done correctly, they will be as strong as or stronger than the aluminum around them. If you pour anything down the standpipe that is heavier than water, it will just keep sinking on out the bottom. If you put something lighter than water, then it should displace the water and stay in place.

GoVols: Pouring cooking oil down the tube should work, as it would float on top of the water and its weight would push the water out the bottom of the intake tube. What’s uncertain here is the likelihood of currents gradually pulling the cooking oil out of the tube. I was also concerned about my through-pontoon water pickups freezing and busting the pipe on the inside of the pontoon. Water froze around my boat three times last winter, but my Marine Air worked just fine to keep the heat rolling inside the cabin. So far, I haven’t had any issues.

boatlover: I took my boat in for general maintenance (anodes, pack shafts, paint, and what not). I had a very small leak on a fitting on the top of one of the standpipes. Their recommendation was to remove the standpipes and install traditional thru hulls. My leak at the standpipe must not have been an isolated incident. They removed and installed sea cocks in place of six standpipes. Now when I close the valve it is down near the hull plane and not a foot or so above. I always worried about if the water in a standpipe could freeze and if it could split the pipe. With no valve at hull level it is impossible to remove the water from the standpipe.

easttnboater: I have also seen the standpipes with an open-topped box welded around them that extends above the waterline. If the standpipe breaks, then the water will just fill the box. It would seem that a combination of traditional thru hulls and the box would the safest. It would also allow you to replace the thru hull while the boat was in the water.

Do you have any questions or advice about standpipes? Hop on the forum and join the conversation.