Waterpump switches on with delay on warm water

[Damir36]

I searched but could not find my problem. When I am running warm water it takes about 10-20 seconds till the fresh water pump switches on when the pressure is way down.

So its no fun in the shower. First it is hot then it gets colder and colder till the pressure is so low the pump switches on and then it is to hot again.

I open the cold water, pump is instantly on, so pump is ok (and only half a year old)
Open warm water, pump takes 15 to 20 seconds to switch on and the water is loosing pressure at this time.
Last year there was no problem and I did not change anything to the water system.

The logical solution would be air in the system or the warmwaterboiler. the air compresses and expands bevor the pump switches on. So I shut of the tank, completely drained the boiler and the warmwatersystem, opened all the faucets, opened the tank and switched on the pump to drive all air out.

No luck... still the same symptoms. Are there any other explanations for this or a different methods to get air out of the system?
(searched for leaks, but found none and the pump is not switching on when all faucets are closed.)

The highest tap where I tried to bleed the system is about 1.5 meters above the boiler so air should come out. I am clueless right now...

Right now I am at anchor and already used 300 of my 600 liters of water trying to get this fixed, and right now the sun isn't cooperating for the watermaker :-)

Thanks Ralph

[Bowdrie]

Does your system have an accumulator tank?
If so, at what point in the system is it located?
If any check valves are in the system, where are they located?

[Damir36]

no accumulator (yet) no check valves. Only the overpressure/drain valve at the quick boiler. One Sink/Shower faucet in each hull and one in the galley

[Tin Tin]

Sounds like a restriction in the hot water plumbing somewhere. Is your faucet standard or a fancy temperature controlled mixer one (so kids don't scald themselves) these can be problematic. If it is a mixer try swapping hot with cold. Try disconnecting the out put from the heater and see if it comes out with decent pressure. Then check further down the line at next join and so on.

[leecea]

You can bypass the water heater by removing the cold water "in" and hot water "out" and connecting them together (drain the heater/boiler first).

If you do this it will help you determine whether the water heater/boiler is or is not the problem.

[Lepke]

Without check valves and an accumulator the hot water can back up the cold line as the water heats.

There are two basic pump switches. The usual one has a high and low setting for off and on. The other starts the pump as soon as the pressure drops and shuts off as soon as high pressure is reached. With an accumulator tank, IMO this works the best for showers.
My pump has both. It normally is the usual high-low. But I switch remotely for showers.

[Damir36]

yeah, thats why I will build in an accumulator as soon as i get my hands on one. But right now i am at Anchor, means that the water does not get heated and it does not explain why it functioned last year. The only thing I did was empty the tank and boiler for the winter, antifreeze was not needed here in Greece.