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Robert Lamoureux: High-pressure hammering

Your Home Improvements

Posted: March 3, 2012 2:00 a.m.
Updated: March 3, 2012 2:00 a.m.


Recently we started getting a rattle and banging sound through the water pipes when we turn on the hot water in the kitchen sink.

This does not happen when we turn hot water on in any other part of the house, and we can get the hot water to run “quietly” in the kitchen if we turn it on the cold first and then slowly move it to the hot side — and only very low pressure.

If you try to turn the faucet on full (with full pressure), it starts to knock and bang. Full pressure on cold works just fine.

Again, this problem only exists in the kitchen — all other faucets (upstairs and down) work perfectly fine — hot/cold/full pressure/no noises.

Is there something you can suggest for us to look for or do to alleviate the problem?

This just starting happening in the last week. Many thanks!

Holly M.


Hi Holly,

This could be one of two possibilities. First I would check the PRV, pressure regulator valve. It may need to be adjusted or replaced.

The maximum permissible amount of pressure is 80 psi. Get a pressure gauge and put it to the water bib outside of your home. Adjust it as needed. The recommended pressure is 70 psi and that should take care of your problems.

Anything beyond that will cause hammering to the pipes. 

We like to keep it between 65 and 70 psi. It helps minimize water waste. If you go up to 80 psi, you’re getting pressure and volume, but you’re also wasting a lot more water.      

If the pressure is at 70 and your getting that banging inside a wall, then, unfortunately, you will have to open the ceiling or wall and restrap the pipe. If left unstrapped, then the movement will break the fittings and cause a leak.

By the way, a friend of mine from the Magic Castle asked me the same question back in the summer of 2007. It was the first question we answered, which began this weekly column, 238 weeks ago.



I’ve got a problem with my toilet. It’s only about 10 years old, but if I don’t keep holding the handle down, then, basically, it won’t flush and I have to use the plunger, which I would rather avoid if I had a choice.

I’m used to it by now, but I will occasionally forget to tell guests and it’s embarrassing.

I agree this is not a big emergency, just more of a nuisance that I hope you know how to fix.

Thank you very much,

Cynthia B.


Hi Cynthia,

It sounds like the flapper is waterlogged. When you flush, the flapper should come up and float long enough to allow water to drain from the tank and into the bowl. But if it’s waterlogged, it’s so heavy that it falls back down and seals off the tank prematurely.

To replace the float, turn the water off at the angle stop and drain the water closet. Remove the flapper. Generally it’s two clips on either side.

Take it down to your local hardware store and match it up because there is an array of those on the market.

Many years ago, there were only one or two styles, but with all of the new toilet manufacturers and styles, there has been a drastic change in flappers recently.

They usually come with a round insert, and if you don’t have it on yours, just break it off in the middle where the two tabs are. You might also have to experiment with it a little and adjust the chain, but it’s an easy fix.  


Hey Robert,

I’m doing my front walkway, and I know I don’t need permits for that.

I want to put in some concrete posts by the street. Do I need permits for that? I want to put in block posts with lights. Thank you,

Ryan R.


Hi Ryan,

You won’t need permits for the pilasters if you keep them less than 4 feet tall, but you will need to permit the electrical. It doesn’t matter how short the distance, if it’s a new electrical run, the city will require permits.

Remember also, before you put a shovel to the ground, you need to first call Dig Alert at 811. Whether for a homeowner or contractor, it’s the law. If you’re caught digging without a Dig Alert ticket, you can be fined $50,000.

Call them two days in advance. They will come out and mark what lines you have underground so you don’t accidentally nick or cut through any lines. 

The color codes they use to mark the underground utilities are:

Red — electric power lines, cables, conduit and lighting cables

 Orange — communication, alarm or signal lines, cables or conduit

 Purple — reclaimed water, irrigation and slurry lines

 Pink — temporary survey markings

 Yellow — gas, oil, steam, petroleum or gaseous materials

 Blue — potable water

 Green — sewers and drain lines

I think you’ll be surprised how shallow some of those lines are, especially out front, where the utilities are coming into the property.


Hi Robert,

I’ve lived here in a condo for quite a few years.

Sometimes in my bathroom I need to flush three times. Sometimes it makes a gurgling noise. Sometimes it doesn’t flush at all, and I need to use a plunger. What do you recommend I do? Thank you,

Felix A.


Hi Felix,

You’re going to have to troubleshoot. It could be a bad toilet or could be due to a partially obstructed vent.

The vent allows sewer gasses to escape, and it also allows air in so you don’t get an upside-down-bottle effect.

If you were to take a bottle of water and turn it upside down, it would chug and come out very slowly. If the bottle is tilted at a slight angle, air gets in and the water flows out smoothly.

Toilets can build up calcium deposits internally over the years, preventing the water from flushing out properly.

You could take a compact mirror and look under the rim of the bowl. You’ll see the jet holes. Take a coat hanger and try to clear those jets. They could be obstructed and preventing a sufficient amount of water to flow down into the bowl.

I remember three years after putting in a new toilet here in Valencia, because of the hard water, I had to replace it. This led me to go with a water softener, and I haven’t had the problem since.

If the jets are clear or the coat hanger makes no difference, it could be that the flapper is waterlogged. If so, it’s too heavy to float and will close quickly, not allowing enough water into the bowl.

Based on the gurgling noise you’re describing, it sounds like you have a vent obstruction. The HOA is going to send a plumber out there and run a snake through the vent, from the roof, down inside the building to clear it.

 We have designed a custom, full-color The Signal/Your Home Improvements T-shirt we will give you if we answer your question. The T-shirt is available to be picked up at our office.

Robert Lamoureux has 25 years experience as a general contractor, with separate licenses in electrical and plumbing contacting. He owns IMS Construction Inc. in Valencia. His opinions are his own, and not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor, after that contractor has made a thorough visual inspection. Send your questions to


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