Just recently the pressure of our water in the house surges when we turn a faucet on, and the city water company verified that our pressure in the house when we open a faucet is higher than the pressure in the lines in the street, and after the water runs is at a normal pressure (meaning their pressure valve is working properly). We are also seeing a significant amount of water coming through the pressure relief valve on the hot water heater. The city water person said we could buy a surge tank to put on the hot water heater to take care of the situation. When I Google "surge tank" I do not find anything that looks correct. Is there something wrong with the hot water tank? What is a surge tank, or does it have a different name?

Look up expansion tank, expansion valve, or expansion toilet fill valve [ballcock]. However, first do a pressure test to find your pressure [psi] on your home. An expansion tank is 30 bucks at home depot. I find the expansion valve to be superior. And if pressure is over 80 psi a pressure reducing valve is required, it is suggest at over 70 psi.

Does this point to a problem that is in the tank itself? What in the tank would cause these symptoms?

It has nothing to do with the tank itself. It sounds like the city recently added the now commonly required back flow preventer to your line. When you use hot water, cold water flows into the tank, expands as it heats, and the excess has to go somewhere. Without the back flow preventer, it could just go back out the cold water line. Now it has to go out the T&P valve until the pressure drops below its setting. That still leaves the system under higher than normal pressure. It was sloppy of the guy to tell you a ''surge tank'' when the proper term is expansion tank as Doug correctly called it.

So you do need an expansion tank or something to allow the excess water out of the tank. If you weren't having problems before, I doubt you now need a pressure regulating valve. You may need a new T&P valve. Once they open, they often get crud in them and never seal. Opening it up might flush the crud out. Soaking it in vinegar to dissolve the lime might work too. Once you have the expansion tank, if it is still leaking, a new one is a sure cure.

If the T&P valve is doing its job, the tank itself should be OK. The valves are designed to to protect the rest of the syustem from excess temperature and pressure.

We do have a backflow preventer, and I think it has always been here, as it is required by the city. The tank is under warranty and I talked to Rheem/Ruud. They said that they need a plumber to call them while he is on site to report findings on different tests. It sounded like the other symptom we would see is that the water would be unusually hot, which I hadn't noticed, but have not measured. If the water is unusually hot, does that point possibly to a problem with the tank not heating to the proper temperature?

We are not discussing the water heater tank, we are discussing the expansion tank which is added to the system typically near the water heater.

Actually, I had two questions initially: 1) Given these symptoms, is there something wrong with my hot water heater, and 2) what was a surge tank. I understand that the surge tank is really an expansion tank, and would treat the symptom of the problem.

I would really like to know why the problem has occurred, and if it points to something broken in the hot water tank, or the valves associated to it. I still do not feel that I understand why the symptoms have occurred when there was no change to the system.

It sounds like the Backflow Preventer required by your local authority has gone points up.

For the life of me, I cannot understand why some municipalities require back flow prevention, which in effect creates a closed system, while not requiring an expansion tank for the inevitable thermal expansion.

Rule of thumb -- If the local authority requires you to create a closed system, thus eliminating an escape route back into the water main for thermal expansion, then whether it's code or not, you should install an expansion tank, if for no other reason than to cover your butt when thermal expansion starts blowing out T&P's, Angle Stops, Shower valves, hose bibbs etc.. .

Calling for a Reduced Pressure Backflow Preventer makes sense, because the over pressure has an outlet -- But a straight Backflow Preventer with no built in relief is just idiotic.

Something here doesn't add up. If you had a back flow preventer and no expansion tank all along, you should have had problems all along. Why was the guy from the city there? Did he come in response to your complaints?

A simple thermostat failure of even bumping the dial could exacerbate the problems of nowhere for the excess water to go. The hotter you heat the water, the more it expands and the more has to go somewhere. You may just be noticing it now that the problem is worse

Hot water tanks are fairly simple things. Yours may have no more of a problem than a bad thermostat and maybe a dirty or weak T&P valve, both worth replacing on a fairly new tank. I don't know that it makes much difference, but is it gas or electric?

It is nice iamgrowler and I can agree on the problem of adding back flow preventers without expansion tanks. Code is code. I really have to fault the city if they instal them without telling the homeowners to add an expansion tank first. In the 4 years I have been here, I have seen a number of problems because of them. It sounds to me like yours is doing exactly what is should.

You should add an expansion tank and check and replace the thermostat and T&P valve if needed.

Quote:

---

Originally Posted by ddewig

Just recently the pressure of our water in the house surges when we turn a faucet on, and the city water company verified that our pressure in the house when we open a faucet is higher than the pressure in the lines in the street, and after the water runs is at a normal pressure (meaning their pressure valve is working properly). We are also seeing a significant amount of water coming through the pressure relief valve on the hot water heater. The city water person said we could buy a surge tank to put on the hot water heater to take care of the situation. When I google "surge tank" I do not find anything that looks correct. Is there something wrong with the hot water tank? What is a surge tank, or does it have a different name?

---

To ddewig,
A surge tank is only used at the highest point of a CLOSED loop heating system. It traps air due to the expansion of the hot water. It would serve no purpose on your set up.
You may need a PRV on your main water line before it goes anywhere else.
Hope this helps.

Quote:

---

Originally Posted by ddewig

Does this point to a problem that is in the tank itself? What in the tank would cause these symptoms?

---

Ddlewig,
If the air leaks out of the tank it can cause problems. Most of the time, however, the tank itself will be leaking water also.

SCjourneyman:

Don't expect an answer or response from anyone too soon. This post is from back in February, 2007... ;)

Have good day! Mark

In a closed system as you have the water in the heater expands when heated. A 50 gallon water heater will produce about 1/2 to 3/4 of a gallon of extra water due to expansion, just like ice does when it freezes. With no place to go it developes pressure and has no place to go. The relief valve is designed to open at 150 lbs to release this pressure. The incoming pressure should not exceed 75 lbs, if it does then a pressure reducing valve should be installed. This makes it a closed system so a expansion tank is needed to handle the extra water due to the expansion of the water from heating. A expansion is available from Lowe's or Home depot, cost about $40-50. This really can be placed any where in the homes water system. The pressure reducer should be installed at the main that feed the entire house not just at the water heater. I have seen where people put in on just the water heater supply, then you get unequal pressure between the hot and cold at valves.

Capt George,
Good answer but you're responding to a two year old post. Check the dates before posting. Regards, Tom

With a backflow preventer, yours IS a closed loop hot water system. To allow for expansion of the water in your hot water system( water, on heating, expands) you HAVE to have an expansion tank (or surge tank- just another name for the same thing)

Hi Antony and welcome to The Plumbing Page on AMHD.
You piggybacked on a 4 year old dead thread Before you post look in the upper left hand corner for the date.. Thanks for your input, Keep posting but check the dates before you do. Regards, bTom

So water from your system does not go back into the cities main, potentially poising everyone else.

Quote:

---

Originally Posted by nickknock

So water from your system does not go back into the cities main, potentially poising everyone else.

---

When I quit laughing at your post I realized you were serious. You are so wrong! Let me count the ways.
1- To put your water back into the city main. You would have to have more house pressure then the city main or have the main shut down and you don't have a mandatory vacuum breaker installed.
2- Where in the world did you ever come up with

Quote:

---

potentially poising everyone else

---

? How do you know your neighbors water's poising everyone if it gets out in the main? Back to Plumbing 101 for you. Cheers, Tom

What is it about this thread that so many people want to keep "resurrecting" it?

Quote:

---

Originally Posted by jlisenbe

What is it about this thread that so many people want to keep "resurrecting" it?

---

I should have deleted his post as silly and not helpful but I wanted to yank his chain and have a little fun doing it. Cheers, Tom