The first thing I would do is contact your gas company and have them come out and give you an opinion.

2nd, if you need to upgrade your meter, we had to pay $1,000 for our new meter and $4,000 for a new gas line because the old gas line wasn't large enough to push the amount of gas we needed from the street to our house. You would have thought our gas utility would have paid for it, but they don't in our area.

When we were getting permits for the 400k gas heater our gas utility determined that we needed to upgrade, not the pool builder. Didn't you have to consult with your gas utility for permit approval?

Sounds like a bargain to at $350.

No permits required where I live (outside city limits). All you have to do here is the Call Before You dig process for them to mark the lines.

I'm not really concerned with the $350 (although it was free until sometime in the last couple of years). I'm more concerned with whether this will fix my problem...or if there is something wrong with the heater.

What model Pentair? In our area, the gas company does not charge for a meter upsize. If you need a larger line, that's a different story from a contractor.

Your beef with Pentair does not hold water. The specs on the heater clearly state the required minimum and maximum gas pressure. Should you need service at anytime on the heater, as long as you are within those specs, you warranty service will proceed. They are under no obligation to offer service if your builder installed outside of specs.

With that stated, if you have an NT heater, this is quite common and the cause is one of three things.

1. Insufficient gas pressure. It may be good when there is no other demand on the meter, but kick on a few other things, and the pressure drop will kill the heater. When it attempts to turn back on, it will fire hard.

2. The burners closest to the igniter may be restricted with spider webs. The gas is injecting into the burner area but not hitting the igniter. When it finally fills the heater and hits the igniter, you get the sonic boom.

3. There is an insufficient air/fuel mixture.

All three of these can be diagnosed by a qualified tech in about 5 minutes and corrected. If the meter is not a 400-425, you're basically wasting your time until you change it.

A pool that is a few months old would really not have an NT. The MasterTemp/Max E Therm runs pretty good out of gas line specs so it is most certainly a pressure issue if that heater is starting real hard.

Thanks for the explanation Repair Guy. I have a MasterTemp. You gave me what I was looking for...someone who knew what I was talking about, and responding confidently that it's a pressure issue.

The problem I was having with both my PB and the Pentair rep is that it really just seemed like a punch list item on a things to try list. The PB kept telling me it is normal ("Yeah, those things really make a loud noise when they start up!"), although he was just responding to my phone calls and I'm not sure he ever really came out to look at it.

The meter upsize (which they do charge for in Houston) is scheduled for Wednesday. I'll post back to make a record of whether it worked or not.

Thanks again.

The noise you refer to is NOT common on that heater. It's a very reliable heater which is why Pentair abandoned the NT which literally "blows".

The odds are just about zero on the burners being plugged as they are sealed. The air/fuel mixture still could be compromised as that is the most sensitive thing on this model heater. You have to go with pressure first even though it may not be the end all.

Another thing you need to look at is the gas line terminations on both ends. You should have a minimal amount of 3/4 pipe at the heater and even less at the meter. As the gas entrance to the heater is typically opposite of what we're used to, meaning it goes to the back of the heater, installers tend to run 3/4 all the way to the main line stub out which can sometimes be 24" or more. This will also choke the heater even with an appropriate meter and line. The same for the meter side. Check for full flow gas valves too on the line. Just to be sure, have the gas guy check the pressure at the heater before he changes the thing out.

I've never had one of those out of the box that did not fire right up.

Most often the gas service and pipe size to the house is more than large enough to handle the meter upgrade in size if necessary. You see, unless you are the rare few, the street gas pressure which can be anywhereÂs from 4-20 PSI is stepped down via a regulator at the meter. A regulator is usually 6-8" in diameter and looks kind of like UFO.
Full capacity gas pipe size to heater before reducing to the 3/4" on the gas entry is crucial.

Once the gas is stepped down in pressure, it is metered and with a slight pressure drop enters your house and supplies your appliances with 5-7" of water column. (1 PSI= 26" water column). This approximant ¼ PSI is all that is needed for your appliances assuming your service and piping can supply the capacity.

The sound that you describe could be resonance at the burner(s). This can happen on heating appliances and very often sounds like a freight train going through your attic or basement, wherever your home heating appliance may be.

Before going off and spending wasted money, a competent gas service man should verify incoming gas pressure at the heater and the manifold gas pressure (at gas valve) with a gauge or manometer while it is firing. Check with manufacturer and rating plate to see what is desired and if it is there and set for it. The incoming can be adjusted a bit at the regulator and the manifold gas pressure can be adjusted on the gas valve if needed. Many people are led to believe that the gas valve is factory set but, how can they know what supply pressure it will be attached to when it can very 2-5" of water column. Also the incoming pressure should be checked with all appliances off and running and if a drop in pressure is noticed, the meter, supply piping, low pressure manifold downstream of meter or piping to heat or all may be incorrect.

In addition and if possible once gas pressures are checked, set or adjusted, if the noise continues, try changing the flow rate through the heater by adjusting bypasses or pump speeds to see if that changes the harmonics. Many tube type (flash) boilers have this problem in the heating industry and flow rates were crucial and needed to be dialed in.

Sounds like you guys know your stuff!

I'm no gas man, but I'm back to thinking this is a "Things to try..." punch list item. Like re-booting a computer.

The only problem I have now is going to be trying to discuss these items with PB and/or Pentair rep, and then trying to figure out if they have or have not evaluated these possibilities. They have nothing to lose by having me upsize the meter first.

Will the gas company evaluate this for me? Is my $350 paying for the meter, the install service, or both?

Thanks for your obvious expert advice!

I'm surprised your gas company charges for that. I live in southern california and I called them up and they sent out a guy to do an evaluation and he said I could use a larger meter after adding up my usage so he came back and installed the bigger meter all of this was totally free of charge. I know this doesn't help you but I would have them evaluate it first before paying bucks for something you may not need. I would think your standard meter should be able to handle your 400K heater, ours did just fine but I had our meter upgraded anyways because we also have a firepit, large BBQ, etc. But if all you are running is your 400K heater and it makes this noise I am not so sure upgrading your meter is going to fix this issue. I think the issue would come up if everything was running at once.

My comments were not to give you a lot of general ideas about heating. I install about many of these models each month and repair very few of them. As I said. The NT gets all of the repair time as it is different technology in the burner system than your heater.

The bottom line is that you have a heater that may need service. The gas guy is not going to diagnose your heater eyond reading pressure and the Pentair guy is not going to look at it without the gas meter. The builder should comply and get this done or at least split the cost. Pentair will not talk to you until you are within specs. The gas guy is coming out and he will check the pressure. I'm guessing the gas guy is not going to get wrapped up inside the heater as this model is a pain in the rump to deal with when it comes to access on the backside. The gas valve is a negative pressure valve and they usually won't deal with all of that when they get into the thing and have to wrestle around the blower, etc.

If he tests the pressure and it is not between 4-14" water column with the heater running, you are undersized.

Water flow is not an issue with what you described. It has a rated minimum flow of 40gpm but they fire without any issue on a low as 28gpm. They do perform best at 80gpm. You said you could hear the heater fire hard for a few seconds while you were down the street. That is a combustion issue. Water harmonics is nowhere near that on this heater and it will be continual but not on start.

You can check some specs in the meantime.

1. For your heater, if you are on any size pipe under 1" and are more than 25' from the meter, you are not installed properly. Keep in mind, that is not a linear measurement of 25'. It could be way shorter based on pipe fittings used.

2. Did they install a flex gas line at the heater? This is also improper.

3. On the gas connections. The street to meter is not an issue. It's the meter AND heater side connections to the line they installed. If you are in excess of 24" of 3/4 line to the main line on either end, you will have issues in firing.

zl700 made mention of a pressure drop as being a problem. Keep in mind that this heater has a normal pressure drop through the valve of 2"wc. Don't get that mixed up with a drop on the meter side when the heater fires.

Finally, the heater does rumble a bit when it fires. It does not sound like an explosion if it is right. It should sound like one of those large propane floor heaters turning on.

repair_guy, here is one for you, I am also building a pool and recently had the gas company come out and swap out my gas meter for a larger one to support my MasterTemp 400 heater. The pool is not finished yet. Over Christmas, I swapped out our 10+ year old water heater in the garage for a new low emissions one from Sears. When the hot water heater kicks on, it emits a low frequency hummmmmmmmmmmmmmm for about 10 seconds. This then transitions to a higher frequency hummmmmmmmm for about 5 seconds and then it goes quiet.

Any suggestions to eliminate this noise would be much appreciated! We can hear it throughout the entire house!

I'd ask a plumber but my initial thought is an issue with the main regulator on he line coming into the house. We get the same type of thing on our house when we run the hose outside which is fed immediately off the low side of the regulator in the garage. When that hose runs, it squeals in the house. Quite possibly air creating in the system through the regulator. I'm guessing the water heater you mention is closest to the regulator and everything down the line is picking up that air. Going quiet after a bit would indicate the air has been purged. Just my guess though.

The weird thing is that the old hot water heater did not make any noise even with the new larger gas meter.

Before you spend the money to upsize the meter (if the existing is a 250K btu the existing unit is too small for that heater) check to see what size and length gas line was installed from the meter to the heater. If the line is undersized a change out of the meter to the larger one won't fix your problem. Instead, have a two stage meter installed (this is way cheaper than new gas line). It regulates the first stage down to a much higher low pressure (5psi?) to allow long gas runs without a restriction and the need for large (2") gas lines. It has a second regulator you would mount right at the heater to get the normal water column pressure. Wish I would have known about it when I did my gas run as it would have saved having to pay for 150ft of 2" line to be installed. Usually the installation manual or owners guide for the heater will have a table specifying min diameter pipe size for any given length. Also make sure thetwo stage regulator installed is 400K btu rated.

Great thread. I am in the process of upsizing my gas line to the house for a water heater addition. There is a separate 1 1/4" line to the spa heater tee'd off the meter from the house line. My plumber said the install is wrong because its about 2-3 feet of 3/4" line off the meter to the 1 1/4" line underground then again 2-3 feet of either black pipe and then CSST line into the pool heater. Our original pool heater was only 333k BTU but I upgrade to the black beehive 400k stay rite. It has that deep rumble whenver it is running. So this reduction to 3/4" off the meter then up to 1 1/4" then back to 3/4" is really a problem?

I feel I can share this info, now that my meter upgrade is completed. I learned to play utilities long ago ex. - cable versus satellite.

I am in Houston also and when I ended up talking to the CNP gas construction dept. rep, I asked him if there as any cost of upgrading my gas meter because I was deciding between a heat pump or gas pool heater. Once he asked who my electric was with (not them), he waived the gas meter upsize charge, and I said go ahead.

Perhaps it cost them some money but, one look at my house and pool, and they know they will get it back in Nat gas usage.

Northern Lights.

If you exceed 18" on the 3/4, you most likely will have issues. The rumble is amplified with insufficient pressure. That heater does best on undersized systems compared to others. I've had them run 50' out of specs w/o issues.

Wow - good thread.

I'm also in Houston, and after 6 months of builder ineptitude am about to be finished. PB couldn't figure out why the heater wouldn't run. Took him 3 weeks to figure out the the meter needed upsizing (I also opted for the pentair master temp). Issue now is that Center Point won't do the swap until they get the final plumbing inspection from the city. I got the green card in the package but the city hasn't sent the proof over yet and the PB is not all that interested in "little details"

It appears to me that the connection between my meter and my heater is a large diameter flex line. It is conneted on the outlet side of the meter (LP side) direct to the heater regulator ball valve.

did I read correctly that this is incorrect or unacceptable?

I had to upsize my Meter by a significant amount (#1to a #4 ) when I installed this heater, the PB told me the gas co would change it NC,.....

..... but the meter was placed in the street and the cement housing could not fit the larger meter!

I had to have the city move the line and mount the meter on the house- then have a plumber come and re plumb the whole house to the new meter.

Guys looking at this heater need a load survey.

Davegvg

I have a 3/4 gas line running about 140 ft from the metre installed by a gas technician. My Gas Pool and Spa heater is 450,000 btu. I have been informed by the pool guy that the pipe should have been 1 1/4" and the Pool Heater will be severaly damaged if I run the heater from the 3/4" line. Is this true? What could happen.

In my area, the cost is based on how much they would charge for construction/installation less how much revenue the utility company believes they can recoup; so It could be closer to zero or upwards to $3-4k for the cost of construction.