Bill & Judy Rouse <yahoogroups@...>
toggle quoted messageShow quoted text
Thanks, Bill. I also thought that the check valve would keep water from back-flowing in pounding seas.
On Wed, Sep 7, 2016 at 9:18 AM, Andrew Lamb andrew.lamb@...
Many thanks – that makes a lot of sense
There is a good reason to use a non-return valve in this application, although it took a little thinking about it before I realized what it is, and it has nothing to do with the outlet side of the pump.
The suction side of the pump shares a saltwater feed with many other pumps. Engine cooling, toilet, watermaker, etc. If there was a restriction in the suction side of the system anywhere, say a partially clogged intake screen, a vacuum
would be drawn and water would flow backwards through the AC pump. This would eventually allow air into the system and break prime for everything.
The AC pump is a centrifugal pump and would offer no resistance to back flow when it is off. Most of the other pumps are, more or less, positive displacement pumps and backflow would be either restricted or impossible.
So, Climmia support is right, the check valve is a potential clog point, reduces flow, and can fail, but it is the small price we have to pay for having a single hole in our hulls!
A take home message is if you are having trouble with raw water feed, remember why that check valve is there and what can happen if it jams open with a tiny piece of trash.
“Ships and men rot in port."
I just put a March magnet drive and kept the non return valve. It works fine, kept the ground wire attached. Very quite and does not get hot.
Bought from Florida, shipped to France. Less than 300€. Came with fittings.
Our AC pump stopped working and I am just about to replace this with an Argal Magnet driven pump recommended by Climma – the original pump has a brass non-return valve fitted to its outlet – and I presume that
this has a purpose. The pump suppliers tell me that this is not required on the new pump and recommend not installing this because of their tendency to get blocked, unless there is a specific installation reason such as a shared outlet. I was wondering if
anyone knows why Amel have installed this – as far as I can work out the outlet is dedicated for the AC water circuit.