Merry Fisher 805 water system

[richlear]

Hi all,

My 2008 MF805 has a hot/cold water system which suddenly stopped working. I found two pumps & filters plus what looks like an accumulator tank? under the sink close to the cold water tank. I cleaned both pump filters but neither were really blocked. I contacted the pump supplier (Jabsco) and they tell me that model of pump (37202-2012) is designed as a sink/shower drain pump and does not have a pressure switch.

There is a switch in the shower to drain the bilge in that area so maybe one of the pumps is for that but i am wondering where the pressure switch for the sink outlet might be so I can check it - Any clues gratefully received!

Thanks

Rich

 

[R400]

Rich galley and heads must have flow switches to operate the boost pumps . There is a small expansion vessel adjacent to the pumps on the starboard side , this will give enough flow to operate the flow switch to kick in the pump. If not the flow switch , wherever they are , the bladders can blow in vessels . Very common problem with heating systems and accumulators.
Won't be at the boat for a couple of days but will investigate if you're not sorted.

 

[richlear]

Thanks - yes there is some sort of expansion/pressure tank right next to the pumps, a white cylinder with domed ends. I have no idea where the flow/pressure switches are though.

 

[Keith-i]

I doubt the second pump is to drain the sink in the galley as that would normally drain via gravity to a skin fitting above the waterline. If the second pump is the water pump then the accumulator will be attached to the outlet pipe just downstream of the pump. The pump will probably have an integral flow switch to turn it on once the pressure in the outlet pipe has dropped sufficiently (i.e. a tap is opened and water is demanded). The microswitch is normally under a cover on the end of the pump and the cut-in pressure can usually be adjusted by turning the screw on the end cap. The accumulator is there to even out the pressure and any pulsing as the pump kicks in.

 

[richlear]

Thanks Keith - I had the same sort of idea in my head but I contacted Jabsco with the pump model number and they tell me that there is no pressure or flow switch on that particular pump, it must be external somewhere.

 

[R400]

Rich had a look at our boat today. There are two pumps for the shower and bilge, one pump for the potable and hot water with the expansion vessel in line before the pump. The pump is a flojet unit, the grey water pumps are jabsco. The flojet Has a live and neutral supply. There are three filters. No more electrical connections in the area.
I think there will be a flow/ pressure switch integral to my flojet , when a tap is opened it is activated by the pressure in the expansion vessel because when running it tends to pulse ie switching in and out to demand. Therefore pump faulty or expansion vessel blown. This is easy to check, if you take it off and it has water in it the bladder is blown. Probably cheaper than a new pump. Available from heating suppliers.
Good luck

 

[R400]

Oh the expansion vessel is there because it's an unvented system. If it is blown it's important it's replaced before the water is heated too much.

 

[richlear]

I checked things out yesterday. The two Jabsco pumps I mentioned are indeed the aft bilge and shower drain. There is a single FloJet further aft, accessible from a hatch in the rear stowage copmpartment which is the water supply pump. I checked the expansion vessel - there was no more than a tablespoon of water in there so I guess the bladder is OK. I looked online and cannot find service instructions or any spares for the particular pump which is a Flojet R4305-505 model. I have contacted the supplier to see what they might have. First thing I want to check is the pressure switch but without a wiring diagram not sure how to bypass the switch to check the pump itself. Next time I go over I will take a little 12V battery with me to play around.

 

[jimmy_the_builder]

There should be absolutely no water coming out of the schrader valve of the expansion vessel. Either the diaphragm is intact, or it isn't. I'd suggest yours isn't.

 

[richlear]

Thanks Jimmy - Maybe I should have been more specific....I do not think there is any water in the tank itself, I think the small amount of water cane from the fitting as I unscrewed it. Is there an easy way to test the tank?

 

[jimmy_the_builder]

Thanks Jimmy - Maybe I should have been more specific....I do not think there is any water in the tank itself, I think the small amount of water cane from the fitting as I unscrewed it. Is there an easy way to test the tank?

Yep; it'll have a sticker on it telling you what pressure it takes; with the pump off and a tap open, use a bicycle pump to pressurise it. Then see if it'll hold pressure.

 

[R400]

Just take it off and shake the water out of it. If water remains in it its inside the bladder, new expansion vessel required

 

[richlear]

Thanks all - was up at the boat last weekend and managed to ascertain that the pump is fine, it was indeed the expansion vessel bladder that had failed. Thanks to all.