dgadee
Well-Known Member
Are diaphragm pumps damaged (overheat etc.) if beyond the pump the outlet becomes blocked? I know they can run dry, but can they run ok when the water in them is not able to exit.
Diaphragm pump query
- Thread starter dgadee
- Start date
No Regrets
Well-Known Member
The 'Gulper' types are diaphragm pumps, and can be run dry with no issues.
Mind you, the Jabsco domestic water pumps can too, which was good news to me when i googled this after my wife ran the boat out of water, leading to the dry pump running for around 6 hours. Still works perfectly much to my surprise!
Mind you, the Jabsco domestic water pumps can too, which was good news to me when i googled this after my wife ran the boat out of water, leading to the dry pump running for around 6 hours. Still works perfectly much to my surprise!
Plum
Well-Known Member
Assuming you are talking about an electric pump and one without a pressure cutout, then if the outlet blocks either a diaphragm or valve could fail or, more likely, the motor will stall. A stalled electric motor will get hotter than a running one and it will either burn out or survive. If it still runs and pumps then you have a robust pump and not likely to have had permanent damage.
Www.solocoastalsailing.co.uk
vas
Well-Known Member
my experience with a gulper 24V one I used as a bilge pump is slightly different...
I had it pumping all right, but some wood chips (boat was still wip at the time) managed to block the skin fitting outlet.
Took me a minute or two to realise it, in that time it managed to mash up the plastic teeth on the crank thing it has to move the diaphragm up and down. Motor was more powerful than the plastic used. Result a broken pump (and spare motor for the second one
The second one I have I use it in a Whale 16lt grey water tank, it's been working fine now for three summers.
so ymmv
I had it pumping all right, but some wood chips (boat was still wip at the time) managed to block the skin fitting outlet.
Took me a minute or two to realise it, in that time it managed to mash up the plastic teeth on the crank thing it has to move the diaphragm up and down. Motor was more powerful than the plastic used. Result a broken pump (and spare motor for the second one
The second one I have I use it in a Whale 16lt grey water tank, it's been working fine now for three summers.
so ymmv
Norman_E
Well-Known Member
my experience with a gulper 24V one I used as a bilge pump is slightly different...
I had it pumping all right, but some wood chips (boat was still wip at the time) managed to block the skin fitting outlet.
Took me a minute or two to realise it, in that time it managed to mash up the plastic teeth on the crank thing it has to move the diaphragm up and down. Motor was more powerful than the plastic used. Result a broken pump (and spare motor for the second one
The second one I have I use it in a Whale 16lt grey water tank, it's been working fine now for three summers.
so ymmv
Try contacting Whale's office in Northern Ireland. When the plastic gear on my Whale Gulper stripped they sent me a new one. Replacement is easy provided the steel worm is OK. In my case the plastic gear stripped because the steel worm rusted and abraded the plastic. Whale sent me both parts and I had to file away the rusted worm to expose the shaft before I could pull it off and force the new one on.
vas
Well-Known Member
cheers Norman, never thought of that, however I'm based in Greece, would that make a difference? should I contact someone somewhere else in the world?
My is practically brand new, hasn't worked more than 20mins, so the steel worm is brand new.
cheers
V.
My is practically brand new, hasn't worked more than 20mins, so the steel worm is brand new.
cheers
V.
jiris
Well-Known Member
All these pumps I know have an inbuilt pressure switch that cuts the power off when the maximum pressure is reached. Switch or not, the fuse should be rated such a way, it would blow when the motor load exceeds the value it is designed for.
A tip: all the pumps I was dealing with experienced a pressure switch failure after a comparably short period of time. The contacts of these switches are grossly underrated and will burn eventually. With this in mind, I am always fitting now a 20 A relay to handle the motor current letting the pressure switch feed only the coil of the relay. Not a single problem since.
vas
Well-Known Member
care to point at such a diaphragm pump? You are not talking about 200quid pumps, but much more expensive, right?
Don't think gulpers have pressure switches and they are not cheap!
cheers
V
vyv_cox
Well-Known Member
There are two principal types of pump, positive displacement and centrifugal. Diaphragm pumps are a type of positive displacement pump. An important difference (amongst many others) is that if a valve is closed downstream a centrifugal pump will not be affected, although it will become extremely hot if run like this for some time, whereas a positive displacement pump will continue to increase the fluid pressure until something breaks, unless it is fitted with a cut-off switch or its design takes this potential problem into account. Think bike pump. Assuming you had the strength to keep pumping, the pressure would just go on increasing until the tyre or connecting hose exploded.
jiris
Well-Known Member
There may be some catch in the type of the pump each of us is talking about. I am not sure about yours, but a typical example of I have on my mind would be this;
https://www.ebay.com.au/itm/Seaflo-...897861&hash=item3b03e94a85:g:GiwAAOSw~7BanPrg .
There are heaps of these (various sizes and quality) on offer and they indeed have inbuilt pressure switches.
It looks like you are talking about "grey water disposal pumps" and they can be a different story. The reason is, the designer simply expects they will be just pumping water out with no significant resistance on the outlet. I looked at the Gulpers, and you are right: they don't have pressure switches, but the distributor is talking about some "electronics" enabling soft start - I would be surprised if it also wouldn't provide an overload protection. You are right, diaphragm pump (unlike centrifugal) pump does get overloaded and if the outlet is blocked. But, if the internal circuitry doesn't provide protection, a simple slow blowing fuse (or circuit breaker) on the power supply would do the job.
vas
Well-Known Member
OK, good,
so all of us are right, but talking about different things!
jiris, like the idea with the separate relay from the freshwater pressure pump though, I'll do it before the summer, thanks!
cheers
V.
so all of us are right, but talking about different things!
jiris, like the idea with the separate relay from the freshwater pressure pump though, I'll do it before the summer, thanks!
cheers
V.