This is not so much a pressure problem as it is a surging temperature problem. When taking a shower, the hot water surges on and off through out the shower process and does not stabilize. We do have an accumulator, about 1 1/2 gallon capacity, just at the water tank exit. We do not seem to see this surging at the galley sink or forward head sink. Do I have any inexpensive options available to me or is this another case of "bite the bullet" and fork over the cash.

If somebody has any ideas, I would appreciate the help. Additional information, if needed, is just a key board away. Thank You

I am not sure from your post about the location of your accumulator, but it should be installed on the discharge line of your water pump. If it is installed on the hot water side of the water heater it will cause the problem you are having.

Rick

I emailed my favorite guru and received this reply:

If the hot water outlet is on the side of the tank, as with all
Raritan water heaters, there is an air space inside the water
heater above the hot water outlet that acts like an accumulator tank. Usually this air becomes entrained into the water, and after a few weeks, works its way out. Then everything is OK.

The only really "permanent" cure is to add another, or a larger accumulator tank in the water pressure system to absorb the pressure variations in the system. Usually it's OK until the pressure pump kicks on - then there's a blast of scalding hot water coming out. (As water is added forcibly to the bottom of the water heater to replace what is being used, the hotter water at the top is being forced out from the pressure of the incoming water). A larger accumulator tank will normally solve this - which is why it doesn't happen in home systems with a well pump, out in the country - the pressure tank is large enough to absorb the variations in pressure.

Coolbreeze -- The accumulator is on the output side of the water pump and is of fairly small volume. Perhaps the internal parts (diaphragm?) that take up the pressure surge have broken and will no longer provide damping.

Peggie -- The output from the water heater is at the lower side of the tank as you have surmised. What concerns me is that no hot water surging is noticed at the sinks in the galley or heads. We only see the surge when someone is taking a shower. I had hoped to alleviate the problem by installing a five gpm pump, but I had neglected to apply a lesson in fluid dynamics. With the same tubing inside diameter as used with the older lower pressure pump, no increase in water pressure would be seen at the shower head. This is what gets me back to the accumulator. It is either to small for the application, or defective. The previous owners did not use the on board water tank because of sickness and ease of using the shore water hook up. This went on for more than two seasons, thus bypassing the water pump and accumulator. If this accumulator is a diaphragm type of device, would it easily rupture after suddenly being used and seeing increased pressure? Is there a non-destructive method to checking out the accumulator?

I've rambled on long enough. Thanks for any help.

"The output from the water heater is at the lower side of the tank as you have surmised. "

You misunderstood....read it again (added emphasis mine): "As water is added forcibly to the BOTTOM of the water heater to replace what is being used, the hotter water AT THE TOP is being forced out from the pressure of the incoming water."

So the input from the fresh water supply has to be connected to the fitting at the bottom of the water heater...the output has to be at the top of the tank.

If your hot water tank is plumbed to receive incoming water at the top and send hot water out a fitting at the bottom, that could very well be the problem.

You are correct! I read it wrong. The water heater is plumbed correctly.with water "in" at the bottom. I was sort of speaking in generic terms.

I'll have to look into another accumulator tank and see what happens. As you know, the area at the output side of the water pump is not all that large so I may have to do some fancy plumbing work to get a larger tank in place.

Thanks for the info. My work list keeps on getting larger and larger.