Shower temperature when running pump

[bravo6]

When my boat is connected to the dock water hose our shower temperature remains constant, when the hose is disconnected and the 12vt pump runs the temperature cools off enough to be uncomfortable. We have an accumulator and when you set the proper water mix the temperature is fine until the pump kicks on,then it's too cold. So a shower on 12vt starts out fine, runs 30-45sec, pump kicks on, now too cold, pump kicks off, temp is ok. The temperature cools down enough that you don't want a 12vt shower. Is this a bad accumulator failing to maintain a uniform pressure in the fresh water system?

 

[Larry M]

Where is the accumulator's located in the system? If you have good water mix for the 30-45 sec. before the pump turns on, the accumulator seems to be working but the location could be the issue.

 

[bravo6]

The accumulator is located almost beside the 12vt freshwater pump on the downstream (output) side of the system, (I think). At any rate I believe it is original system by the builder,,so I thought something was worn or not working. Boat is 10 years old and I see no evidence of parts switched around.

 

[Bay Pelican]

10 seconds is a key. I am wondering whether you are setting your temperature based on the water that is in hoses. The water contained in the thin hoses would by ambient heat be a different temperature than water which is in the accumulator or in the tank. The volume of the water would affect the temperature.

A way of testing this would be to see if you have the same results if you run the water at the dock without having used the boat and thus heated up the hoses.

Marty

 

[mahal]

My guess would be that the pump supplies the shower mixer with more pressure than the hose. When the pump comes on, the hot to cold ratio is then changed.

 

[bravo6]

I won't say you're on to something, but I don't understand your reply. Shower works good on ''dock'' water, so the lines are at a constant temp. The water heater, pump and accumulator are on the other side on the bulkhead from the shower controls so the ''run'' is negligible. On 12vt shower the ambient temp of the fresh water storage tank would be the same as the accumulator tank because they are in the same machinery space. I think the pump puts more water volume in the system than the accumulator does thereby making you feel cold water (though you can't feel a pressure/volume difference in the shower head). The accumulator pressure/volume and the 12vt pump pressure/volume are not the same and I don't understand why.

 

[bligh]

I can help you resolve this, but first i need you to run only the hot water in the shower for a few minutes when you are not connected to the dock water.. No cold water. What happens to the water temperature then? Does the temperature fluctuate or remain constant?

 

[bravo6]

Hello bligh, We must do this in theory, as here on Lake Erie, I have pulled my boat for the winter, It is in heated storage unit and I am 175 miles from it. I am interested in what your thoughts are, so what are you thinking?

 

[LaBomba]

Because the hot and cold water lines are separate and have a different path, number of elbows, hot water tank etc., the flow through each line will vary depending on pressure. On a dock hookup it would be fairly constant and thus the stable temperature/pressure. On the DC pump the only way I have found to get around this pressure/flow imbalance is by installing a temperature compensating or pressure balancing shower control valve. We had the same issue on our fifth wheel RV as well. Have a look at this link. They are available at all big box stores like Home Depot but will mean a little work to install.

KOHLER | How to Shop for Shower Valves and Controls | How to Shop for Bathing Products | How to Shop Bathroom Products | Bathroom Ideas & Planning | Bathroom |

 

[FF]

The dock water has a set pressure that does not vary much.

Your accumulator is basically to save the pump as it cycles off , and to hold some of the pressure created when you heat water from cold to hot.

The system pressure will vary probably from 20 psi on cut in to 40 psi at cut out,or 30-50psi.

This changes the temperature you feel.

IF you have the room a 6 (or larger) gallon home well style accumulator will do a far better job , as the temp will change slowly as you use that 6 gal.

Remember to drain it for the winter.

Some of the more modern pressure pumps claim to make a constant flow with no accumulator , borrow one from a dock mate and find out.

 

[BobH]

Get rid of the cycling pump and accumulator and put in one of the variable speed pumps.

Bob