Bilge Pump Non-Return Valve

[smurphny]

One negative about diaphram pumps is that they are noisy. I have one as a backup on a separate circuit but, mounted on the bulkhead, it sounds like a helicopter landing. They will pump out more water than a centrif. type pump with a good foot strainer.

[Blue Stocking]

Originally Posted by smurphny

One negative about diaphram pumps is that they are noisy. I have one as a backup on a separate circuit but, mounted on the bulkhead, it sounds like a helicopter landing. They will pump out more water than a centrif. type pump with a good foot strainer.

They are noisy for sure. I can easily access mine thru a large partial bulhhead accessed from my cockpit locker. Keep a Phillips #2, with screws, belt and diaphram set in a ziplock bag tied to the outlet side.

[Safari38LH]

Had the same problem and ended up putting a Rule 500 with a check valve and reduced outlet hose of 1/2 inch below a manual Rule 4000 with no chck valve. Also added high water alarm on top of the 4000. I have a small deep bilge. Budge nice an dry now. Had to use an older Rule 500 because the new one with the oil sensor would not turn off automatically.

[roverhi]

I put a non return valve in my bilge pump for the same reason as you. I've got a pretty high loop in the hose so it won't back syphon which dumps a fair amount of water back in the bilge when the pump shuts off. It's worked fine for about a year but stuck open, doubt that it would ever stick closed, last week. The non-return valve is not an install and forget it solution to your problem but will stop the immediate issue of constant cycling of the pump. I wouldn't not install one worried about the valve sticking closed and not allowing the pump to evacuate the water.

[Capitain Mike]

Originally Posted by simonmd

In that case, adjust the float switch so that any water running back into the bilge doesn't trigger it again. As most pumps like this work on the impellor principal, they are incapable of completely pumping them dry completely, only a proper suction pump can do that.

Exactly

[Capitain Mike]

Originally Posted by roverhi

I put a non return valve in my bilge pump for the same reason as you. I've got a pretty high loop in the hose so it won't back syphon which dumps a fair amount of water back in the bilge when the pump shuts off. It's worked fine for about a year but stuck open, doubt that it would ever stick closed, last week. The non-return valve is not an install and forget it solution to your problem but will stop the immediate issue of constant cycling of the pump. I wouldn't not install one worried about the valve sticking closed and not allowing the pump to evacuate the water.

My (Stupid) question to Jabsco

From: Mike Macloughlin
Sent: 22 January 2011 10:56
To: mail@jabscoshop.co.uk
Subject: Help Please 19mm non return valves used in a bilge system


Hello.

Please help me I have a stupid question I have several (3) of your 19mm one way bilge non return valves fitted into a bilge system all on one pipe all fitted before I bought the boat.
are these all necessary?

I had a problem that the bilge pump would not pump even though it was spinning so I replaced it with a rule 360.

This 360 works ok and pumps out through a temporary pipe without a non return valve.

Between the time of the problem and the fitting of the pump I had disconnected the non return valve closest to the pump.

Now I do not know which end of non return valve should go to the pump or the outlet.

When I connect the non return valve to the new pump no water goes through it. so I don’t know if it is the valves not working or the pipe blocked


Part no::: 29295-1011

Mr Mike Macloughlin

Thank you

You are better off having no non-return-valves in the discharge of the pump (3 is ridiculous!). Try without any, if you find you get a problem with water running back to the bilge then try and see if adding one back helps, though it may be too much for the pump.

Easiest way to find the direction an NRV operates in is to try and blow through it, you should find more resistance one way than the other.

Best regards
Jon Paterson
JABSCOshop.com, FLOJETshop.com, LVMshop.co.uk, Cleghorn.co.uk

P Please consider the environment before printing this email




--------------------------------------------------------------------------------
From: Mike Macloughlin [xxxxxxxx@hotmail.com]
Sent: 22 January 2011 10:56
To: mail@jabscoshop.co.uk
Subject: Help Please 19mm non return valves used in a bilge system

SO NO NON RETURN VALVES.
If worried about water ingress when heeling fit a swan neck just higher than and just before the thru-hulloutlet

[Dockhead]

Thanks for all the useful suggestions! I hope this thread will help a lot of people.

I have about come to the conclusion that -- as several people suggested -- my Rule 4000's should be mounted a little higher as crash pumps so that unless there is some kind of emergency, or if the primary pump fails, they will simply never come on. Thus no non-return valve is necessary.

And to replace the primary pump. The choices are (a) a traditional diaphragm pump like the Jabsco, (b) a Whale Supersub 1100; (c) one of the new Whale diaphragm pumps -- this one: Marine : Whale Pumps 12V Henderson Plumbing Bilge Diaphragm Submersible Pressure Water Systems Marine Caravan RV Shower Drain Portable Sanitation Purging Groundwater Solutions Voltage Electric

I like the fact that the Supersub -- a centrifugal pump -- pumps 1100gph (nominal) -- a significant amount of water. So it's not just a "maintenance pump". The switch is built in and has intelligent control with soft starting, delays, etc. And a non-return valve is built-in. I don't insist on absolutely dry bilges, because mine are deep and narrow at the bottom -- a little water in the bottom is no big deal. As a bonus, the Supersub is dirt cheap.

Of the two diaphragm pumps, I think I favor the Whale one -- it doesn't depend on a separate float switch, and it has all of the intelligent controls of the Supersub. The problem with the diaphragm pumps is that they pump too little water to be considered anything but a maintenance pump, plus they are about 400% the cost of the Supersub.

[westsail42]

Originally Posted by David M

Never feed two or more pumps into a common discharge port.

I'll have to disagree with this one. Installing a separate thru-hull and seacock for each bilge pump is quite impractical if not expensive. Each pump discharge line should have their own loops, but combining them after the loop, near the thru-hull should be perfectly fine. If you are in a position to increase the size of the thru-hull, even better (example, 1/2 inch discharge + 1 1/2 inch discharge into 2 inch thru-hull is ideal).

[PhilK]

The easiest thing to do would be to fit a check valve. Check valves have 2 failure modes - fail to open - fail to close. Fail to open generally occurs on small valves <1" where the surface area of the seal is large compared to the surface area of the valve and the psi can't overcome the stiction. With a 2" hose and a good pump you shouldn't have a problem. Fail to close leaves you where you are already. If the outlet is well above the waterline - and it should be - you won't have any insurance problems. Just flush it through with clean water on an annual basis.

The other option is a delay off time switch. This could be set to allow the pump to run for, say, 10 seconds after the level switch has tripped. Needs a separate supply to keep the contact closed.

Third option is another level switch set lower than the first. The current switch trips a relay which is held on by the lower switch. The relay will then keep the pump running until the second switch is off. You will still get water coming back but it won't reach the first level.

You are concerned about your batteries. All of the above apart from the check valve involve repeatedly pumping out reflushed water. I'd go for a check valve. If you're really worried it may be worth considering wiring a very high level switch to your horn and telling a friend in the marina that if the horn sounds your boat is about to sink!

[GordMay]

Greetings and welcome aboard the CF, PhilK.

Most bilge pump manufacturers, and I (), recommend against the use of check valves in BP discharge lines.

[Blue Stocking]

IMHO, bilge pump manufacturers advise against non-return valves for two reasons.

1st. They presume that an installer will make up an assembly that will fit into the hose size and therefore, further restrict their flow figures. These figures are generally not realist anyway, being determined with no head lift, no hose friction loss, and a fully charged battery. Remember, they rate them in gallons PER HOUR.
To remove 4000 gallons in an hour (thats 1 1/2 oil drums a minute) is going to require a substantial battery bank, and un-impaired pump circumstances.
Read their fine print.
So, IMO, build a non-return valve assembly that provides FULL hose bore opening THRU the valve. Thats what I have done, but using belt driven pumps.
Also, the brass ron-return valves often used because of easy availability, have clappers that are very heavy. This is because they are designed to withstand high pressures in plumbing systems. Remove the clapper and grind away most of the excess weight on the non-sealing side of the casting. This will reduce the resistance that the pump will have to overcome, and assist the flow.

2nd. Restrictive impediments in the discharge hose increases the risk of blockage, and creates a situation of "who dun it" in the event of a sinking.
Lawyer country, pump builders don't want to go there, if their $150 pump sunk your $200,000 + yacht.
Negate this "fun" scenario, by building proper baskets with large flow areas around your submersible pumps.
Door and window manufacturers, who build intrusion resistant products often use stainless or monel 8 x 8 per inch mesh. Thats what I use.

And, talking about lawyers, What I have opined above, works on my boat, but may provide different performance on yours.

[Dockhead]

This seems like great advice and I hope it helps other sailors.

I decided against a non-return valve, although I find the comments above by PhilK and Bluestocking to be really convincing.

Just because I already have a separate small bilge pump which can be easily swapped for a maintenance pump. The big Rules get their float valves mounted higher and become crash pumps. The Whale Supersub 1100 becomes the primary pump, and moves enough water to ensure that the Rules won't ever even come on unless there is some really big problem.

Otherwise I would go for a non-return valve as suggested.

[PhilK]

Whale (who are one of the biggest bilge pump manufacturers) say (in the fitting instructions for the Supersubs)
"Fit an in-line non-return valve to prevent back filling".

They also manufacture the Strainer IC "with integral non-return valve".

In an ideal world you wouldn't need an NRV - I haven't on my boat because I have a short, small diameter hose to the skin fitting and the back fill cleans the filter on the bilge pump (experience from my garden pond!). The original poster has a problem which I feel would be solved painlessly with an NRV. You pays your money and you takes your choice.

[psneeld]

Installing check valves with centrifugal style bilge pumps is a big mistake….ANY resistance to a centrifugal bilge pump or the mere head one must pump starts t drastically reduce its capacity.
A diaphragm pump for maintenance then high capacity for emergencies is clearly the preferred solution by experts.

[PhilK]

Well Whale (manufacturer of centrifugal type pumps) clearly disagree with you - and they should be experts.

Another solution might be to reroute the hose to go vertical to start with and fit an anti-siphon bend so that only the short vertical length back fills. It may not be practicable though seeing that the original installation was "involved".

Rule say that reducing the hose diameter is acceptable (will just reduce the capacity). Reducing the hose to 38mm will reduce the back flow by approximately 40% which should effectively stop the problem.