Another fresh water pump question

[Ka_sea_ta]

In order to make the pressurized water system on the boat more reliable and robust I'm looking for some opinions. The boat has two heads, each with a shower and fresh water flush toilet. Also has a washer dryer, large galley sink, ice maker, cockpit wash down and requires fresh water for the water maker flush. The current pump is variable speed 4 gpm diaphragm pump that is pretty anemic with more than 1 fixture using water. The pump manufacture does not recommend using an accumulator. So is there any reason I couldn't put an additional VSP in parallel. My thinking is this would make the existing system more robust and provide redundancy in case one pump fails.

 

[Taras]

Yes, putting another pump fitted with valves in parallel is done very frequently so you can rapidly switch over to the back up pump (if the current one fails). I've never had a boat without an accumulator tank however...... I think those help a lot with regulating the pressure to ensure constant pressure and to reduce the number of pump cycles. You may also consider switching to a higher GPM pump

 

[Don L]

In 7.5 years of living on my boat full time with 2 people my system with an on/off pump and accumulator tank has needed no maintenance

 

[tiltrider1]

Your problem is flow rate. You should be looking at a screw pump instead of a diaphragm pump for increased flow rate. I have all the same demands as you have listed. I have no issues, I use a Marco UP12e which has a 9.5 gpm flow rate.

While the Marco is a variable speed pump, I highly recommend using an accumulator with it.

 

[Ka_sea_ta]

I know that flow rate is an issue, hence my question. While the existing VSP is around 4gph the one other I want to place in parallel is 5 gph I plan on running both pumps at the same time.... I had planned on putting an inline check valve on the outlet side of the pump that shut off first (lowest pressure) I just don't what the down side is if I do this. TIA

 

[O C Diver]

I know that flow rate is an issue, hence my question. While the existing VSP is around 4gph the one other I want to place in parallel is 5 gph I plan on running both pumps at the same time.... I had planned on putting an inline check valve on the outlet side of the pump that shut off first (lowest pressure) I just don't what the down side is if I do this. TIA

Probably don't need a check valve as the exhaust valve on the outlet of the pump will do the same thing.

Need to check the plumbing coming from the water tank(s). 1/2" pipe won't support 9 GPM. Depending on your current plumbing, you might want to start with increasing the plumbing from the tank to the pump. Pumps push water but don't suck it well with flow restriction from small convoluted plumbing. If I were designing a boat, all the plumbing from the tank to the pump would be 1".

Ted

 

[Bmarler]

Your problem is flow rate. You should be looking at a screw pump instead of a diaphragm pump for increased flow rate. I have all the same demands as you have listed. I have no issues, I use a Marco UP12e which has a 9.5 gpm flow rate.

While the Marco is a variable speed pump, I highly recommend using an accumulator with it.

I thought the Marco was a gear pump, not a screw. I’m looking at using the up6 ( I think) when my current pump fails.
I think galley maid made a screw pump, but my memory is a little hazy on that.

 

[tiltrider1]

I thought the Marco was a gear pump, not a screw. I’m looking at using the up6 ( I think) when my current pump fails.
I think galley maid made a screw pump, but my memory is a little hazy on that.

As I look at Marco’s drawing it is a gear pump. The gears are screw shaped and this is what I always remember.