Toilet flushing water pressure reducer

[Gunna Do]

I've recently replaced a leaky water pump with one of similar spec. I now have full water pressure in the system but flushing the loo causes water to shoot over the top of the bowl and onto the floor. This happens when the accumalator is at full pressure but stops as soon as the pressure falls a lttle. I need to put a pressure reducer in the inlet water pipe. I've so far got no reply from Thetford nor can I find a part number in their spares list. I presume that this is just a nylon plug with a hole in, that goes into the inlet water pipe. Does anyone have one they don't use or can give me dimensions so I can turn one up? I could of course use a pipe clamp but that tends to damage the plastic pipe after a time.

Graham

[WotEver]

The optional pressure reducer that came with a washing machine we bought a while back simply halved the pipe diameter. I'd imagine the Thetford one is similar, but I'm sure someone will come along in a while who has one spare kicking around.

 

Tony

[LEO]

I've recently replaced a leaky water pump with one of similar spec. I now have full water pressure in the system but flushing the loo causes water to shoot over the top of the bowl and onto the floor. This happens when the accumalator is at full pressure but stops as soon as the pressure falls a lttle. I need to put a pressure reducer in the inlet water pipe. I've so far got no reply from Thetford nor can I find a part number in their spares list. I presume that this is just a nylon plug with a hole in, that goes into the inlet water pipe. Does anyone have one they don't use or can give me dimensions so I can turn one up? I could of course use a pipe clamp but that tends to damage the plastic pipe after a time.

Graham

 

Hi,

 

Do you have an isolating valve in the pipework serving the fitting?, if so (and if not it would be wise to fit one in case of emergency) turn this down a bit to reduce pressure.

 

Should overcome the problem.

 

If it works you will now have to find another excuse for the ladies for a wet floor!.

 

Leo.

[WotEver]

Do you have an isolating valve in the pipework serving the fitting?, if so (and if not it would be wise to fit one in case of emergency) turn this down a bit to reduce pressure.

 

Should overcome the problem.

Very good point. Why do I always miss the bleedin' obvious?

 

T

[AlanH]

Very good point. Why do I always miss the bleedin' obvious?

 

T

Just a pedantic point. A restriction will not decrease the pressure but it will cut down the flow.

Edited July 14, 2010 by AlanH

[RLWP]

Just a pedantic point. A reducer will not decrease the pressure but it will cut down the flow.

 

I have been trying very hard not to make the same pedantic point. I decided that as long as the reducer was close to the toilet, the time taken for the pressure difference to develop across the reducer wouldn't make any difference

 

Richard

[WotEver]

I have been trying very hard not to make the same pedantic point. I decided that as long as the reducer was close to the toilet, the time taken for the pressure difference to develop across the reducer wouldn't make any difference

 

Richard

Where's the smiley for 'over my head' when you need one?

 

I'll make do with this:

[RLWP]

Where's the smiley for 'over my head' when you need one?

 

I'll make do with this:

 

Consider the following. A pump, a reducer, a tap.

 

With the tap shut, the pressure after the pump is what the pump can generate. There is no flow, so the pressure after the reducer will become the same as the pump pressure (you can imagine less and less water creeping through the reducer until the pressure equalises)

 

If you open the tap, the pressure after the pump is what the pump can generate. The reducer restricts the flow and creates a pressure drop, so the pressure after the reducer is lower than the pump pressure (which is what was wanted in this case).

 

Reducers only lower pressure when there is flow.

 

So, with the toilet, there will be an instantaneous bit of flow at full pump pressure, dying away to the pressure permitted by the reducer (there's another opportunity for pedantry here, and I'm not going there). My guess is it won't be noticed

 

Does that bring it down to the level of your head?

 

Richard

[WotEver]

Does that bring it down to the level of your head?

 

Richard

Yeahhhhhh... I think so... (he says, with the cloudy look still in his eyes). So if the reducer was close to the solenoid valve (your 'tap'), the effect of the flow restrictor would indeed be for it to act as a pressure reducer for the purposes of the OP's question? If it was further away from the valve then the initial 'surge' would still have him wetting the floor. Correct?

 

I've seen the result of your description on our boat since we've fitted an inline water filter. We have no accumulator and have never previously found a need; we turn a tap on and the pump operates more or less continuously until we turn the tap off. Now with the new water tap that's fed by what amounts to an effective ceramic flow restrictor when we turn on the tap we get an initial surge of water, then the pump operates, then the pump turns off etc so we get a 'pulsed' water supply. I'm now considering where I could fit an accumulator.

 

Tony

[RLWP]

Yes, you've got it, and as you say, your filter does the same thing

 

Richard

[alan_fincher]

Hi,

 

Do you have an isolating valve in the pipework serving the fitting?, if so (and if not it would be wise to fit one in case of emergency) turn this down a bit to reduce pressure.

Yes,

 

This works.

 

I was going to introduce the Thetford bit into the pipe, as our flush can be a bit enthusiastic at times, but partially turning the isolator ball valve allows you a variable adjustment, so I never bothered.

 

(The Thetford part has a surprisingly small hole in it, BTW, maybe a maximum of only 3mm in diameter. I had my doubts it would flush enough if I used it).

[Tony Brooks]

Yeahhhhhh... I think so... (he says, with the cloudy look still in his eyes). So if the reducer was close to the solenoid valve (your 'tap'), the effect of the flow restrictor would indeed be for it to act as a pressure reducer for the purposes of the OP's question? If it was further away from the valve then the initial 'surge' would still have him wetting the floor. Correct?

 

I've seen the result of your description on our boat since we've fitted an inline water filter. We have no accumulator and have never previously found a need; we turn a tap on and the pump operates more or less continuously until we turn the tap off. Now with the new water tap that's fed by what amounts to an effective ceramic flow restrictor when we turn on the tap we get an initial surge of water, then the pump operates, then the pump turns off etc so we get a 'pulsed' water supply. I'm now considering where I could fit an accumulator.

 

Tony

 

 

Just one thing to consider about accumulators. They will not prevent the pump cycling on and off. The only way to do that is to ensure the outlet is capable of passing a greater volume of water than the pump can deliver at a given pressure. Then it will not cycle but run continuously. An accumulator will lengthen the cycling rate though but I suspect it will not stop in because for the filter.

[WotEver]

Just one thing to consider about accumulators. They will not prevent the pump cycling on and off. The only way to do that is to ensure the outlet is capable of passing a greater volume of water than the pump can deliver at a given pressure. Then it will not cycle but run continuously. An accumulator will lengthen the cycling rate though but I suspect it will not stop in because for the filter.

Hi Tony,

 

I wasn't imagining that an accumulator would stop the pump from cycling, just that it would allow it to cycle less. Are you agreeing that it would do that?

 

Tony

[ditchcrawler]

Very good point. Why do I always miss the bleedin' obvious?

 

T

You mean the pan?

[LEO]

You mean the pan?

Which brings us 'nicely' back to wet floors.

 

Leo

[Tony Brooks]

Hi Tony,

 

I wasn't imagining that an accumulator would stop the pump from cycling, just that it would allow it to cycle less. Are you agreeing that it would do that?

 

Tony

 

Yes, and the larger the accumulator the longer the cycling period.