Does this type of manual tap have a non return valve?

[ProDave]

We find our water tank apparently runs dry quicker than expected, when you fill it, not much goes it. So we investigated today, expecting to find the pickup hose was not at the bottom. But we found something else instead.

Both the sink and the basin have this sort of tap, which I think is Whale, but can't actually see anything on them to confirm that.


Each tap has it's own hose that then tee together into a single pipe into the water tank. Once the tank gets part empty, instead of drawing water from the tank, it sucks air in from the other tap. Put your finger over the spout of the unused tap and the other one pumps okay.

So are these taps supposed to have a non return valve built in (if so it has failed) or did the original plumber of this system just do it all wrong?

 

[PeterV]

I don’t believe it does have a non return valve. I have the same on my heads sink and I have to have an isolation valve on the pipe to it. otherwise the freshwater tank drains through the tap when I’m heeled over on port tack!

 

[ProDave]

I will try buying 2 in line non return valves so hopefully the other tap won't admit air down it's spout when I pump the other. Much easier than trying to re plumb the tank for each to have it's own hose all the way and own pickup pipe.

 

[Daverw]

I would expect some sort of non return valve or they would not pump when pressed down and just move water back and forth

 

[B27]

I don’t believe it does have a non return valve. I have the same on my heads sink and I have to have an isolation valve on the pipe to it. otherwise the freshwater tank drains through the tap when I’m heeled over on port tack!

That's not a lack of 'non return' it's water flowing the correct way through the pump.

There is a non return valve in mine, it stops the water in the pipe draining back to tank level, which is a fair bit lower than the sink.

 

[ProDave]

When you pump the sink tap, you expect it to suck water up the pipe. It does that. But instead of then sucking water out of the tank, because they are teed together, it is sucking water DOWN the pipe connecting to the basin tap and drawing air in the basin tap.

So if there is supposed to be a non return valve built in, it has failed. And as this happens regardless of which tap you pump, any such non return valve has failed?

 

[Daydream believer]

2 pipes - 2 new taps. At £ 37 each for the taps it is a no brainer really

 

[B27]

That design of tap has been around for a very long time.
Not really surprising there's a few worn out examples around!

 

[rogerthebodger]

Those type of taps do have some kind of NON-Return valve in fact 2 of then.

The problem you may have is either a worn NRV or some crud trapped in the valve holding it slightly open thus allowing water to return. They could also just be worn of rubber seals perished

 

[srm]

At some time the system presumably worked. Get two service kits and replace all the perishable parts. If that does not solve the problem then isolation valves (as you suggested) will.

 

[Geoff Wode]

I had similar on my boat. Replacing all the fittings (inc taps), pipe work and valves with push fit Whale came to around £200. Couple of hours easy work and will probably do another 30yrs.

 

[Bodach na mara]

The answer to the question lies in understanding basic science, specifically physics. Not the subjects that you learn in school, but a more cynical version of which the basic laws are:- If it's dead, it's biology. If it smells it's chemistry. If it doesn't work, it's physics.
Lift pumps like the ones you are considering incorporate two non-return valves. They don't actually work unless there is a fair old bit of back pressure because they belong to the physics part of science. So in practice, with only a few cm. of water over the valves, they leak back allowing air in. It is also the reason that, even with only one in the system, you need to pump like buggery to get it primed and delivering water.

 

[VicS]

I will try buying 2 in line non return valves so hopefully the other tap won't admit air down it's spout when I pump the other. Much easier than trying to re plumb the tank for each to have it's own hose all the way and own pickup pipe.

They have valves in them (they would not work without) but they are not very good so I'm not surprised by the trouble you are having especially if they are a few years old.
Non return valves in the pump suctions should solve the problem but you might find it difficult to prime the pumps initially if the valves are too strongly held shut. ( even non return valves are physics )

 

[Daverw]

On our last boat we had two of these type, one stopped pumping, when I stripped it it had a small ball as a NRV that was clogged with scale/ sludge. Cleaned it and it worked again but eventually changed it and fitted a pump

 

[William_H]

As said open up the pump(s) and clean out the ball NRV at the bottom of the main tube. This should hold the water there for next use as well as permitting proper operation of the pump. If you can't get it apart and back together av a noo one. (or 2) ol'will

 

[ProDave]

I have taken the easy way out and ordered 2 in line non return valves. Way cheaper than replacing the taps, and servicing them would require me finding out what model they are and so far I have seen nothing on them to identify them.

So the next question, where is the best place for the in line NRV's. at the bottom near the tank? or at the top just under the tap?

 

[Boathook]

I have taken the easy way out and ordered 2 in line non return valves. Way cheaper than replacing the taps, and servicing them would require me finding out what model they are and so far I have seen nothing on them to identify them.

So the next question, where is the best place for the in line NRV's. at the bottom near the tank? or at the top just under the tap?

I would fit where ever is easiest which is possibly near the tank ?

 

[ghostlymoron2]

I would fit where ever is easiest which is possibly near the tank ?

I have taken the easy way out and ordered 2 in line non return valves. Way cheaper than replacing the taps, and servicing them would require me finding out what model they are and so far I have seen nothing on them to identify them.

So the next question, where is the best place for the in line NRV's. at the bottom near the tank? or at the top just under the tap?

It's a Whale type V pump. I've had several of these on caravans and small boats. I don't think whale make them or spares any more but there are many clones. You can hear the ball type nrv rattling if you shake them. Best solution is to dismantle, clean and reassemble.

 

[LittleSister]

So the next question, where is the best place for the in line NRV's. at the bottom near the tank? or at the top just under the tap?

I believe they will be most effective if they are as low as possible, i.e. near the tank, just beyond the split between the two hoses. Here they will have the weight of the water in the pipe above holding them closed, but it would probably work with them higher, near the taps.